ok, i have my bro's old thunderchicken and I'm trying to correct a few things on it so that I can sell it. it has been doing that noise for a quite some time, don't know exactly when it started. It varys with rpm, so I'm thinking alternator wiring maybe or grounds, but not certain. it's a '91 thunderbird with a completely stock stereo. if I sell it then I've got some more money for other projects. any help would be greatly appreciated.