here's a list i compiled from random threads from here or other sites. have no personal references with any of them but generally all seem to be recommended by someone er other. dutch treat seems to be the most reasonable from places i've called so far.
dutch treat porsche
rob
15200 Inglewood Ave
Lawndale, CA 90260
(310) 644-1006
TRE motorsports
Dave, Jeremy
11046 Chandler Blvd,
North Hollywood, CA 91601
818 509 0257
www.tremotorsports.com
NARW
klaus
7355 Canby Ave.
Reseda, CA 91335
Tel. 818.881.1222
Scientific Automotive
(626) 795-7018
1727 E Walnut St
Pasadena, California 91106
http://www.scientificauto.com
foreign sport technicians
claudio
1301 Broadway
Santa Monica, CA 90404
Phone: (310) 394-0369
info@foreignsporttechnician.com
Mueller Motors
2934 W Main St
Alhambra CA 91801
626-281-7860
200 North Motorworks
1842 South Robertson Boulevard
Los Angeles, CA 90035
(310) 558-3394
the Speed Gallery
11550 Ventura Blvd.
Studio City, CA. 91604
1-818-766-2321
game-face motorsports
601 e. lambert rd.
la habra CA 90631
562 694 3880
Stuttgart Automotive Service
19841 Valley Blvd.
Walnut, CA 91789
909-595-1936
stuttgartsvc@earthlink.net
http://www.stuttgartautoservice.com