I have a 2000 Ford F-150 and it seems
to be a problem with Fords. I dont know that it is a much the amp picking up
the
radio signal or the speakers/wires.
I have a Kenwood stereo, no amp, and
a 6 CD changer....gets into it as much as
the stock one did, whether it is On or Off..
I was told to try ferrite chokes on the speaker wires....as soon as i get the
door panels off....one of these days!

"Got RF?"