Mark - for my "higher" end cars I've always used Speed Industry since Alexei took it over. They're in Troy. Before buying the QP I asked if it was a car he could work on. He does my friends lambos, my 911TT, etc.
If you run a search for MI service or repair shops there have been previous threads on this topic. Cauley and Auto europe seem to be cheaper than Suburban. There were also indy shops in farmington and warren that had good reviews.
If I can find the info on those I will repost.