Gen 5 Camaro Tuning, Diagnostics, Dyno results - 2012 camaro ss tune?????!!

So i have just finished adding kooks long tubes, k&n intake, and flowmaster catback.
I'm now ready for a tune.
Located in southern cal, wheres the best place, and what numbers should i expect to see out of this ls3?
My check engine is perminately on since the headers at only 4000 miles. Gm sayin theres too much flow. will a tune help this problem?

You should see 410-420 at the tire with a good tune and your mods.