It took me a few years to realize this, but the service while courteous, don't necessarily find the problem with the car. Two examples:
1. Had a rear tire that was leaking air. Audi reportedly did all the tests to find a leak but told me that no leak was found . I was then told that there must not be a leak and to keep an eye on it. Of course, the tire kept leaking air. Took it to another shop who found a leak and fixed it.
2. Ever since we got the car the brakes squeaked. Even with changing brakes, the squeakiness continued. Audi said they did "all the tests" , and found no reason for the squeaking. They suggested that once in a while to slam on the brakes hard, to see whether this could "dislodge" whatever was causing the squeaking. Of course this did nothing. When my brake pads needed to be replaced, I took it to another shop. Now the squeaking is gone.
While the service people are nice to speak with, I've lost all confidence in their ability to diagnose problems.