You may or may not have stumbled onto it, but there's a thread, "Find your local mechanic/porsche specialist", that talks about this subject. I went through it, found 4 hits/recommendations for the San Diego area. Two are no longer around, two are still hangin' in there:
Black Forest Automotive https://www.blackforestautomotiveca.com/
Dieter's https://www.dietersmotorsports.com/
I can't personally say anything one way or the other about these two shops—I live at the other end of the country. But someone here on the forum thought well enough of them to make the recommendation.