yeah i had same problem turned out to be bad grounding then a bad altenator and rcas picking up noise so i ran the rcas opposite from the power lines... also i shield everywhere and buy the highest quality i can afford then i shield it some more with electrical tape.... also you can try one of those isolators i forget there actual name but they sell them at radioshack u can get one to try and isolate all of that feedback noise in the entire electrical system or the kind where you can isolate it just for the rca lines ... i used to work for radioshack the company sucks but some of there things are ok
