Third attempt at conditional gzip decoding based on the Content-Encoding response header with the mikeal/request library for Node.js. Based on Mikeal's code.

gzipRequestStreams.js

var request = require('request'),
  zlib = require('zlib'),
  fs = require('fs');

var headers = {
  "accept-charset" : "ISO-8859-1,utf-8;q=0.7,*;q=0.3",
  "accept-language" : "en-US,en;q=0.8",
  "accept" : "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
  "user-agent" : "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_6_8) AppleWebKit/537.13+ (KHTML, like Gecko) Version/5.1.7 Safari/534.57.2",
  "accept-encoding" : "gzip,deflate",
}

var options = {
  url: "http://google.com",
  headers: headers
}

var compressedRequest = function(options, outStream) {
  var req = request(options)

  req.on('response', function (res) {
    if (res.statusCode !== 200) throw new Error('Status not 200')

    var encoding = res.headers['content-encoding']
    if (encoding == 'gzip') {
      res.pipe(zlib.createGunzip()).pipe(outStream)
    } else if (encoding == 'deflate') {
      res.pipe(zlib.createInflate()).pipe(outStream)
    } else {
      res.pipe(outStream)
    }
  })

  req.on('error', function(err) {
    throw err;
  })
}

// Dummy write stream. Substitute with any other writeable stream
var outStream = fs.createWriteStream('./sample.html')
compressedRequest(options, outStream)