I have the bose speakers and what not installed on my car and I decided I wanted to upgrade to an aftermarket headunit so I could get xm and usb and whatnot. Well I got it installed with the metra wiring harness, but the sound is very low and my rear speakers don't work at all. I posted on my6thgen and someone said I needed to get the PAC Roem-Nis2. I ordered it, but am wondering... Does it replace the metra wiring harness, or is it just "added on"? Thanks for your help!

 

I believe it is added on but I'm not 100% sure