[lm6y]

I'm guessing that it is the whining that sounds like a siren type noise.

99% of noise in a car stereo is caused by a ground loop. It sounds like the Stilletto is getting a different ground than your radio. That's called a ground loop. It will pick up whatever ground has the least amount of resistance back to the battery.

Try moving the ground for the stilletto around. If it runs off the cigarette lighter plug, try grounding the radio to that. If you have it hard wired, try attaching the ground to the radio chassis.