This question is regarding my 2000 Audi A6 2.7 Turbo that is out
of warranty and has 50,000 miles.

Question: I recently had new brakes installed by my longtime
mechanic who knows little about german cars.  Now the brakes squeel
and whistle when the car is in bumper to bumper traffic or approaching
a stop light (like the sound of a braking bus or a 18 wheeler). If I
apply the brakes hard, no squeeling but as I let up on the brakes,
they sing. I realize the brakes were likely not installed properly and
I need to find a qualified audi mechanic, but why specifically do my
brakes sing like they do?

By the way, I am trying to maintain a high precision automobile on a very low
budget (I know, good luck). If you happen to know an honest,
reasonably priced audi mechanic in the boston area, let me know.