I have a '95 E420 with factory everything. I just recently got the factory cd changer off ebay and plugged it in. Everything works fine except there is the engine whine that changes pitch with the rpm's, only when I am playing a cd. There was never any noise before and now it is only during cd playback.

What could be the problem? Is it a bad ground in the cd changer wiring? What should I try? Where do I look? Etc. Please help me to get this fixed as it is very annoying. Thank you.

this is usally bad wiring , more like a ground situation. You have some wiring that is touching somehwere in your car that is recieveing some engine (wav) noise.

Very annoying, you probably hear it when you have the turn signals turned on too?