gulp stream.push

[Георгий Катерняк]

#gulp #plugin.
Hi ) I'm not a javascript guru, so ...
I've already made the task, but have problems with the speed
I stacked with stream.Transform.push. Here is test code

var fs = require("fs"),
    through2 = require("through2"),
    Transform = require("stream").Transform,
    vinyl = require("vinyl"),
    async = require("async");

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.
.
resolveDependant = function(file, stream, cb){

         /**
         * @var array tree - list of files[], aka driectory tree
         */
        var reg = new RegExp("Catch me!", "gm"),//ignore
            seriesList = []; //for threading

        for(var f in tree){

            seriesList.push( //ignore
                function(file){ //ignore
                    return function(callback){ //ignore
                        fs.readFile(file, { encoding : "utf8" }, function(err, data){ //ignore
                            if(reg.exec(data)){ //trying to catch him!
                                stream.push( //here is time leak! For 4 files it spent 1.6s.
                                    new vinyl({  //without previous line it spent 0.4s for same 4 files
                                        path : file,
                                        contents :
                                            new Buffer(data)
                                    })
                                );
                            }
                            callback();
                        });
                    }
                }(tree[f])
            );
        }

.
.
.
       this.chain = function() { //gulp.pipe(obj.chain()) call
        return through2.obj(function (file, enconding, cb) {
         /**
         * @var array tree - list of files[], aka driectory tree
         */
            if(!tree.length) //just ensure that chain was called after initialization
                return cb(null, file);

            var stream = this;

            resolveDependant(file.path, stream, function(){
                stream.push(file); //test mode ignore any input
                cb(); //return control to pipe
            });
        });
    }

Can anyone explain me why it spent so much time to push vinyl files into stream

stream.push( ... );

Any help, books, advices and etc. will be helpfull.
Thanks