For what it's worth, the Trusted TDI Mechanics by State thread is pretty outdated for Arizona. Can't seem to get anybody to update it or provide good shops. Updates recommended years ago haven't been made. It's a shame. That being said, Autobahn Motorwerks up in North Phoenix still has a good reputation, especially if Derek is still working there (used to own Exklusiv Motorsports on that mechanics thread). He's come and gone a little, and there's a thread on here bashing him about a single job gone wrong, but I and other people I trust have all had great experiences with him. As of a year ago, he was still the cheapest timing belt job in the state, though he was talking about raising his rate. And unfortunately, he's like an hour drive from me. Independent Automotive, the other one on the list, shows as permanently closed.
I got so frustrated with finding a TDI mechanic I just decided to figure out how to do most of it myself. Now, even when I don't do it, I know what to tell a shop I want done.