[Bigdrumma22]

As mentioned, check grounds, run main power wire seperately from the RCA cables. I've been able to get away with running my remote wire with the RCA's because it is such a small wire and I use good shielded RCA's. By interference, do you mean you get a high pitched whine in synchronous with the engine RPM's? If that is the case, try those things. Also, what kind of small amp are you using? If you are using a cheap no name brand just to get by, I might try a higher quality amp if you know a buddy that has one or happen to have an extra one to test it. I originally started my first stereo system in my old truck with an ebay amp special and well, it sucked. As soon as I put in a nice new pioneer amp, all noise gone, everything else wire wise was untouched. Just changed the amp, and problem solved. That's just my experience. Hope this helps.