About a month ago I had the borla stingers installed up at LAPD. Along with the stingers I already had a vararam intake. LAPD did a dyno tune for me. I went from 358hp to 377 with 371 ftlb torque. Contact Shawn at LAPD he can hook you up with a good deal.
There is a dyno shop on Prospect in Santee and one at the Beamer shop over by the stock car track in El Cajon, but from what I have been told neither shop seem to be really up on getting the most out of the LS1 edit program, I live not that far from either of these dyno shops but I will take my Z up to either LAPD or A&A to get dyno tuned once I get headers, these guys seem to know how to pull the most HP from a Z.
If you get tuned by one of the local shops let us know how you made out.