well it's something that's been pissing me off for some time now... sometimes i notice it when my volume is low, and i'm driving around... so i was searching for how-to's and found this:

02-16-04

FUEL SYSTEM—FUEL PUMP “WHINING”/“BUZZING” NOISE COMES THROUGH ENTERTAINMENT OR TWO-WAY RADIO SPEAKER

RADIO—ENTERTAINMENT OR TWO-WAY COMMUNICATION—“WHINING”/“BUZZING” NOISEIN SPEAKERS CAUSED BY FUEL PUMP

NOISE—“WHINING”/“BUZZING”—COMES THROUGH SPEAKERS OF ENTERTAINMENT OR TWO-WAY RADIO

it's a ford service bulletin.. so i figure i'll give it a shot. anyone else notice this?

 

Ive got the same bloody problem....Im not sure if you need a resistor or more grounds but this happens too Fords. I wish ford would copy GM's harness cause this never happen to GM.
Every time I put a large stereo in a car it goes into a GM only.
Good luck and when you find the problem let me know and I might start turning my stereo back on in the Stang.