Park Ave motors is very reputable, but you pay and pay and pay and pay for service there (I think labor is north of $100/hr now).
Bought my car there, but I take it to Auto Haus Los Gatos now - Herr Schwager is great and their labor is a *bit more reasonable* (boy that was hard to type) at $80/hr.
I'd call them and ask for a referral to the SF location - you probably don't want to commute all the way down here and there HAS to be a good tech in the city, Oakland or Berkeley (easy BART access).
MB Doc and Steve: NO good MB techs (though lots of MBs) on Maui or Oahu - after all these years no less. Getting tired of the south yet?