I just installed a Kenwood Excelon 8120 dvd/navigation unit in my 2003 Chevy Silverado w/Bose and onstar using an Axxess GMOS-04 wiring harness. Everything is working great and the sound quality is awesome, but I'm getting feed back through my speakers when I touch the brake pedal. What should I do to fix this?? Ground, wires touching??? I've tried taping up all rca cables and unused wires.