PV Bikes is a reputable place. They do Specialized BG fittings.

In Los Angeles, I'd recommend Nate Loyal (Helen's/Santa Monica), Ted Ersnt (Ted's/Manhattan Beach), and the guys at Cynergy (Santa Monica) or Surf City Cyclery (Huntington Beach). If you are near the SG Valley, Stan's Monrovia Bikes does Serotta fittings.

I'd stay away from Performance as if it were the plague.