Heres A weird One - Reverse and Radio
 

On the 98 zr2, just noticed this today, when ever i put my truck in reverse with the radio on, the radio will cut out for a second or two. i dont loose power to the radio, the screen stays lit. but the sound quickly fades in and out when put into and out of reverse. as if the antena signal is being intruputed. this does not happen when im playing a CD. and the radio is stock. The only thing i have done to the reverse light circut is tap off of that for my back up camera relay, But i installed that months ago and today i first noticed this problem. I also installed a radar detector a few weeks back. The reverse circut controls the back up camera relay. I taped off the power from the parking light circut for my radar detector and power for the camera. any input would be apperciated!

I would unhook the b/up camera wiring and see if the problem still exists and go from there. If corrected possibly tap off something else but for now..unhook and see. I also realize you said this has been wired this way for awhile but who knows why things show up when they do..good luck-Jerry