Platte Forme a.g. (Automotive Group) is in Alhambra, not too far from L.A. I like The R's Tuning in Irvine too if you're willing to drive further.
PF won't be good for anyone in a major rush though, they're preparing for Global Time Attack series and have reduced the number of customers they have scheduled until April 22nd due to prep work and testing for their race car. Just an FYI if you have a hard time getting a hold of them. Email
Gary@platteformeag.com if you want to give it a shot though.