Quote Originally Posted by mlchael4 View Post
Were the stock speakers not hooked up to the factory wiring? I don't know why else you wouldn't be able to balance the speakers F/B & L/R.
Hooking up a sub to a factory HU does require an in-line converter...but those should be the only RCA's wired to that converter.

Also, did they run the RCA's and power cables on the same side of the car?
That can cause interference right there. Is the amp properly grounded? All of these details can lead to hissing and undesirable noise.
They car was stock before...so I'm pretty sure it was hooked up to factory wiring...they replaced all that though. They ran power and RCA on opposites sides.

This thing is whats going from the HU to the amp.

http://www.discountcarstereo.com/detail.aspx?ID=753