Hey Mike,
You seem to have some knowledge on radio issues in the Audi(s), so I was hoping you may be able to bounce some ideas with me. I have a 2002 A4 (1.8T) Avant. When I got it the sound from the radio would cut in and out (radio is on fine). This occurs randomly, but also definitely when I hit bumps or change gears. After research and looking over the car, it seemed that it was most likely the drivers door wiring harness (several wires were stripped and taped or reconnected). I replaced the wiring harness (probably needed to be done again), but this did not solve my radio problem. I've read that the amp could be out, but because the sound goes off (or on) when I hit bumps or change gears, etc., I believe it is more likely a loose wire somewhere. I'm thinking it's under the dash, and will be looking there today. But wondered if you had any other ideas? Thanks for the time and attention, Forrest