diff --git a/src/functions/demux.ts b/src/functions/demux.ts
index 0ad2e57..a9b1011 100644
--- a/src/functions/demux.ts
+++ b/src/functions/demux.ts
@@ -31,15 +31,10 @@ export function demux(
 }
 
 class Demux extends Writable {
-    public isWritable: boolean;
     private streamsByKey: {
-        [key: string]: {
-            stream: NodeJS.WritableStream | NodeJS.ReadWriteStream;
-            writable: boolean;
-        };
+        [key: string]: NodeJS.WritableStream | NodeJS.ReadWriteStream;
     };
     private demuxer: (chunk: any) => string;
-    private nonWritableStreams: Array<string>;
     private construct: (
         destKey?: string,
     ) => NodeJS.WritableStream | NodeJS.ReadWriteStream;
@@ -57,26 +52,19 @@ class Demux extends Writable {
         this.demuxer = demuxBy.keyBy || ((chunk: any) => chunk[demuxBy.key!]);
         this.construct = construct;
         this.streamsByKey = {};
-        this.isWritable = true;
-        this.nonWritableStreams = [];
     }
 
-    // Throttles when one stream is not writable
     public async _write(chunk: any, encoding: any, cb: any) {
         const destKey = this.demuxer(chunk);
         if (this.streamsByKey[destKey] === undefined) {
-            this.streamsByKey[destKey] = {
-                stream: this.construct(destKey),
-                writable: true,
-            };
+            this.streamsByKey[destKey] = this.construct(destKey);
         }
-        if (!this.streamsByKey[destKey].stream.write(chunk, encoding, cb)) {
-            await new Promise((resolve, reject) => {
-                this.streamsByKey[destKey].stream.once("drain", () => {
-                    resolve();
-                    this.emit("drain");
-                });
+        if (!this.streamsByKey[destKey].write(chunk, encoding)) {
+            this.streamsByKey[destKey].once("drain", () => {
+                cb();
             });
+        } else {
+            cb();
         }
     }
 
@@ -87,7 +75,7 @@ class Demux extends Writable {
                 break;
             case EventSubscription.All:
                 Object.keys(this.streamsByKey).forEach(key =>
-                    this.streamsByKey[key].stream.on(event, cb),
+                    this.streamsByKey[key].on(event, cb),
                 );
                 break;
             case EventSubscription.Unhandled:
@@ -107,7 +95,7 @@ class Demux extends Writable {
                 break;
             case EventSubscription.All:
                 Object.keys(this.streamsByKey).forEach(key =>
-                    this.streamsByKey[key].stream.once(event, cb),
+                    this.streamsByKey[key].once(event, cb),
                 );
                 break;
             case EventSubscription.Unhandled:
diff --git a/src/functions/map.ts b/src/functions/map.ts
index c088c72..13834af 100644
--- a/src/functions/map.ts
+++ b/src/functions/map.ts
@@ -12,12 +12,7 @@ export function map<T, R>(
     return new Transform({
         ...options,
         async transform(chunk: T, encoding, callback) {
-            try {
-                const mapped = await mapper(chunk, encoding);
-                callback(null, mapped);
-            } catch (err) {
-                callback(err);
-            }
+            callback(null, await mapper(chunk, encoding));
         },
     });
 }
diff --git a/tests/demux.spec.ts b/tests/demux.spec.ts
index bde4ffe..aedbe6c 100644
--- a/tests/demux.spec.ts
+++ b/tests/demux.spec.ts
@@ -172,63 +172,6 @@ test.cb("demux() should send input through correct pipeline using keyBy", t => {
     demuxed.end();
 });
 
-// Probably needs to be removed
-test.cb("should emit errors", t => {
-    t.plan(2);
-    let index = 0;
-    const input = [
-        { key: "a", visited: [] },
-        { key: "b", visited: [] },
-        { key: "a", visited: [] },
-        { key: "a", visited: [] },
-    ];
-    const results = [
-        { key: "a", visited: [0] },
-        { key: "b", visited: [1] },
-        { key: "a", visited: [2] },
-        { key: "a", visited: [3] },
-    ];
-    const destinationStreamKeys = [];
-    const sink = new Writable({
-        objectMode: true,
-        write(chunk, enc, cb) {
-            expect(results).to.deep.include(chunk);
-            expect(input).to.not.deep.include(chunk);
-            t.pass();
-            cb();
-        },
-    });
-
-    const construct = (destKey: string) => {
-        destinationStreamKeys.push(destKey);
-        const dest = map((chunk: Test) => {
-            if (chunk.key === "b") {
-                throw new Error("Caught object with key 'b'");
-            }
-
-            const _chunk = { ...chunk, visited: [] };
-            _chunk.visited.push(index);
-            index++;
-            return _chunk;
-        }).on("error", () => {}); // Otherwise ava complains
-
-        dest.pipe(sink);
-        return dest;
-    };
-
-    const demuxed = demux(
-        construct,
-        { keyBy: (chunk: any) => chunk.key },
-        { objectMode: true },
-    );
-    demuxed.on("error", e => {
-        expect(e.message).to.equal("Caught object with key 'b'");
-        t.pass();
-        t.end();
-    });
-    input.forEach(event => demuxed.write(event));
-});
-
 test("demux() when write returns false, drain event should be emitted after at least slowProcessorSpeed * highWaterMark", t => {
     return new Promise(async (resolve, reject) => {
         t.plan(7);
@@ -259,11 +202,14 @@ test("demux() when write returns false, drain event should be emitted after at l
             },
         });
         const construct = (destKey: string) => {
-            const first = map(async (chunk: Chunk) => {
-                await sleep(slowProcessorSpeed);
-                chunk.mapped.push(1);
-                return chunk;
-            });
+            const first = map(
+                async (chunk: Chunk) => {
+                    await sleep(slowProcessorSpeed);
+                    chunk.mapped.push(1);
+                    return chunk;
+                },
+                { highWaterMark: 1, objectMode: true },
+            );
 
             const second = map(async (chunk: Chunk) => {
                 chunk.mapped.push(2);
@@ -285,14 +231,6 @@ test("demux() when write returns false, drain event should be emitted after at l
             reject();
         });
 
-        _demux.on("drain", () => {
-            expect(_demux._writableState.length).to.be.equal(0);
-            expect(performance.now() - start).to.be.greaterThan(
-                slowProcessorSpeed * highWaterMark,
-            );
-            t.pass();
-        });
-
         let start = null;
         for (const item of input) {
             const res = _demux.write(item);
@@ -301,6 +239,11 @@ test("demux() when write returns false, drain event should be emitted after at l
                 start = performance.now();
                 await new Promise((resolv, rej) => {
                     _demux.once("drain", () => {
+                        expect(_demux._writableState.length).to.be.equal(0);
+                        expect(performance.now() - start).to.be.greaterThan(
+                            slowProcessorSpeed * highWaterMark,
+                        );
+                        t.pass();
                         resolv();
                     });
                 });
@@ -318,63 +261,60 @@ test("demux() should emit one drain event when writing 6 items with highWaterMar
         }
         const highWaterMark = 5;
         const input = [
-            { key: "a", mapped: [] },
-            { key: "a", mapped: [] },
-            { key: "a", mapped: [] },
-            { key: "a", mapped: [] },
-            { key: "a", mapped: [] },
-            { key: "a", mapped: [] },
+            { key: "a", val: 1, mapped: [] },
+            { key: "a", val: 2, mapped: [] },
+            { key: "a", val: 3, mapped: [] },
+            { key: "a", val: 4, mapped: [] },
+            { key: "a", val: 5, mapped: [] },
+            { key: "a", val: 6, mapped: [] },
         ];
         let pendingReads = input.length;
         const sink = new Writable({
             objectMode: true,
             write(chunk, encoding, cb) {
                 cb();
-                t.pass();
                 pendingReads--;
+                t.pass();
                 if (pendingReads === 0) {
                     resolve();
                 }
             },
         });
         const construct = (destKey: string) => {
-            const first = map(async (chunk: Chunk) => {
-                chunk.mapped.push(1);
-                return chunk;
-            });
+            const pipeline = map(
+                async (chunk: Chunk) => {
+                    await sleep(50);
+                    chunk.mapped.push(2);
+                    return chunk;
+                },
+                { highWaterMark: 1, objectMode: true },
+            );
 
-            const second = map(async (chunk: Chunk) => {
-                chunk.mapped.push(2);
-                return chunk;
-            });
-
-            first.pipe(second).pipe(sink);
-            return first;
+            pipeline.pipe(sink);
+            return pipeline;
         };
         const _demux = demux(
             construct,
             { key: "key" },
             {
                 objectMode: true,
-                highWaterMark,
+                highWaterMark: 5,
             },
         );
+
         _demux.on("error", err => {
             reject();
         });
 
-        _demux.on("drain", () => {
-            expect(_demux._writableState.length).to.be.equal(0);
-            t.pass();
-        });
-
         for (const item of input) {
             const res = _demux.write(item);
             expect(_demux._writableState.length).to.be.at.most(highWaterMark);
             if (!res) {
-                await new Promise((_resolve, _reject) => {
+                await new Promise(_resolve => {
                     _demux.once("drain", () => {
                         _resolve();
+                        expect(_demux._writableState.length).to.be.equal(0);
+                        t.pass();
                     });
                 });
             }
@@ -386,8 +326,8 @@ test.cb(
     "demux() should emit drain event immediately when second stream is bottleneck",
     t => {
         t.plan(6);
-        const highWaterMark = 5;
-        const slowProcessorSpeed = 200;
+        const slowProcessorSpeed = 100;
+        const highWaterMark = 3;
         interface Chunk {
             key: string;
             mapped: number[];
@@ -395,11 +335,13 @@ test.cb(
         const sink = new Writable({
             objectMode: true,
             write(chunk, encoding, cb) {
+                expect(chunk.mapped).to.deep.equal([1, 2]);
                 t.pass();
-                cb();
+                pendingReads--;
                 if (pendingReads === 0) {
                     t.end();
                 }
+                cb();
             },
         });
         const construct = (destKey: string) => {
@@ -408,16 +350,13 @@ test.cb(
                     chunk.mapped.push(1);
                     return chunk;
                 },
-                { objectMode: true },
+                { objectMode: true, highWaterMark: 1 },
             );
 
             const second = map(
                 async (chunk: Chunk) => {
-                    pendingReads--;
                     await sleep(slowProcessorSpeed);
                     chunk.mapped.push(2);
-                    expect(second._writableState.length).to.be.equal(1);
-                    expect(first._readableState.length).to.equal(pendingReads);
                     return chunk;
                 },
                 { objectMode: true, highWaterMark: 1 },
@@ -440,8 +379,9 @@ test.cb(
 
         _demux.on("drain", () => {
             expect(_demux._writableState.length).to.be.equal(0);
-            expect(performance.now() - start).to.be.lessThan(
-                slowProcessorSpeed,
+            // Should take longer than the amount of items needed to be processed until we are under highWaterMark
+            expect(performance.now() - start).to.be.greaterThan(
+                slowProcessorSpeed * (input.length - highWaterMark - 1),
             );
             t.pass();
         });
@@ -453,18 +393,18 @@ test.cb(
             { key: "a", mapped: [] },
             { key: "a", mapped: [] },
         ];
-
         let pendingReads = input.length;
+
+        const start = performance.now();
         input.forEach(item => {
             _demux.write(item);
         });
-        const start = performance.now();
     },
 );
 
-test.only("demux() should only emit drain event when all streams are writable", t => {
+test("demux() should be blocked by slowest pipeline", t => {
     t.plan(1);
-    const highWaterMark = 2;
+    const slowProcessorSpeed = 100;
     interface Chunk {
         key: string;
         mapped: number[];
@@ -476,33 +416,26 @@ test.only("demux() should only emit drain event when all streams are writable",
                 cb();
                 pendingReads--;
                 if (chunk.key === "b") {
-                    expect(performance.now() - start).to.be.greaterThan(150);
+                    expect(performance.now() - start).to.be.greaterThan(
+                        slowProcessorSpeed * totalItems,
+                    );
                     t.pass();
-                }
-                if (pendingReads === 0) {
+                    expect(pendingReads).to.equal(0);
                     resolve();
                 }
             },
         });
         const construct = (destKey: string) => {
             const first = map(
-                (chunk: Chunk) => {
+                async (chunk: Chunk) => {
+                    await sleep(slowProcessorSpeed);
                     chunk.mapped.push(1);
                     return chunk;
                 },
                 { objectMode: true, highWaterMark: 1 },
             );
 
-            const second = map(
-                async (chunk: Chunk) => {
-                    await sleep(2000);
-                    chunk.mapped.push(2);
-                    return chunk;
-                },
-                { objectMode: true, highWaterMark: 1 },
-            );
-
-            first.pipe(second).pipe(sink);
+            first.pipe(sink);
             return first;
         };
         const _demux = demux(
@@ -510,6 +443,7 @@ test.only("demux() should only emit drain event when all streams are writable",
             { key: "key" },
             {
                 objectMode: true,
+                highWaterMark: 1,
             },
         );
         _demux.on("error", err => {
@@ -521,13 +455,21 @@ test.only("demux() should only emit drain event when all streams are writable",
             { key: "a", mapped: [] },
             { key: "c", mapped: [] },
             { key: "c", mapped: [] },
-            { key: "b", mapped: [] }, // should only be recieved after a and c become writable
+            { key: "c", mapped: [] },
+            { key: "b", mapped: [] },
         ];
 
         let pendingReads = input.length;
+        const totalItems = input.length;
         const start = performance.now();
         for (const item of input) {
-            console.log("DEMUX", _demux.write(item));
+            if (!_demux.write(item)) {
+                await new Promise(_resolve => {
+                    _demux.once("drain", () => {
+                        _resolve();
+                    });
+                });
+            }
         }
     });
 });
@@ -543,6 +485,7 @@ test("demux() should emit drain event and first should contain up to highWaterMa
         const sink = new Writable({
             objectMode: true,
             write(chunk, encoding, cb) {
+                expect(chunk.mapped).to.deep.equal([1, 2]);
                 t.pass();
                 cb();
                 if (pendingReads === 0) {
@@ -557,7 +500,7 @@ test("demux() should emit drain event and first should contain up to highWaterMa
                     chunk.mapped.push(1);
                     return chunk;
                 },
-                { objectMode: 2, highWaterMark: 2 },
+                { objectMode: true, highWaterMark: 1 },
             );
 
             const second = map(
@@ -568,7 +511,7 @@ test("demux() should emit drain event and first should contain up to highWaterMa
                     pendingReads--;
                     return chunk;
                 },
-                { objectMode: 2, highWaterMark: 2 },
+                { objectMode: true, highWaterMark: 1 },
             );
 
             first.pipe(second).pipe(sink);
diff --git a/tests/map.spec.ts b/tests/map.spec.ts
index 75210ff..35c8e84 100644
--- a/tests/map.spec.ts
+++ b/tests/map.spec.ts
@@ -49,61 +49,3 @@ test.cb("map() maps elements asynchronously", t => {
     source.push("c");
     source.push(null);
 });
-
-test.cb("map() emits errors during synchronous mapping", t => {
-    t.plan(3);
-    const source = new Readable({ objectMode: true });
-    const mapStream = map((element: string) => {
-        if (element !== "b") {
-            throw new Error("Failed mapping");
-        }
-        return element.toUpperCase();
-    });
-    source
-        .pipe(mapStream)
-        .on("data", data => {
-            expect(data).to.equal("B");
-            t.pass();
-        })
-        .on("error", err => {
-            source.pipe(mapStream);
-            mapStream.resume();
-            expect(err.message).to.equal("Failed mapping");
-            t.pass();
-        })
-        .on("end", t.end);
-
-    source.push("a");
-    source.push("b");
-    source.push("c");
-    source.push(null);
-});
-
-test("map() emits errors during asynchronous mapping", t => {
-    t.plan(1);
-    return new Promise((resolve, _) => {
-        const source = new Readable({ objectMode: true });
-        const mapStream = map(async (element: string) => {
-            await Promise.resolve();
-            if (element === "b") {
-                throw new Error("Failed mapping");
-            }
-            return element.toUpperCase();
-        });
-        source
-            .pipe(mapStream)
-            .on("error", err => {
-                expect(err.message).to.equal("Failed mapping");
-                t.pass();
-                resolve();
-            })
-            .on("end", () => t.fail);
-
-        source.push("a");
-        source.push("b");
-        source.push("c");
-        source.push(null);
-        source.push(null);
-        source.push(null);
-    });
-});