[s-cars] Engine-radio interference

[Bob Frizzell]

S-Men (Gentlemen):
I'm getting interference from my engine through my radio speakers - a whistling sound when the engine is revved. It goes away briefly if I turn the radio off and then back on.  Hell, it goes away completely if I don't turn the radio back on!  I seem to recall dealing with this in a former life (the '65 Mustang in my youth, maybe).  What is the fix, guys?
Always appreciative,
Bob, 93 //S4
Playing in the snow in Edmonton