I have a 2002 mustang and recently installed an after mark head unit which created some problems. I have a Pioneer Deh-x3500ui and now I receive no bass from my back speakers and have engine noise coming from the speakers. I went to Car Tunes and they told me reason was because of the factory amps and that I would need to rewire my car to remove these problem. I was wondering if anyone had any knowledge on re wiring speakers like the best kind of wire to use, any info would be helpful. Also I have a Kenwood Kac-1502s laying around and I was wondering if it would be better to swap out the stock amps and replace it and if that would get rid of the engine noise. Also the factory amps will get warm after 15 or so minutes so I know they are getting power to them, just no bass in playing. Also I know they work because when I hook up my factory head unit they will play bass. Also there's a resistor on the blue wire, I can't remember what kind it was, do I need it there or can I just remove it.
Here's a picture of the wiring harness: imgur.com/a/nMaO4