Avoid both Auto Alpina and Berkely Auto Services. I had terrible experiences both places. I like Tomas, but as stated, they are expensive. Precision People's in Berkeley works on TDIs. I used to get work done from one of their mechanics "on the side." Unfortunately, he's changed his line of work. The mechanic around the corner from me at Alfa Automotive in East Oakland works on diesels and is super-affordable, but doesn't like to get involved w/anything too complicated (and is not a specialist). My deepest frustration w/owning my TDI has been inability to find a good local mechanic.