There is www.gmtuners.com
. I have been working with them for a few months.
reccomending what i did, but so far:
I'm shifing at 6400<--too high blah blah i don't want to hear it
Tuned close to 100% for L67 injectors and L67 maf
removed evap code
and some other stuff i can't think of right now.
The bad part is that it'* impossible to get all this right done in the first shot esp. when it'* not done in person. But gm tuners won't stop sending me updated chips till i'm satisfied 100%. Plus it'* only like 40 bucks i think.
But a custom chip isn't going to do too much without major mods besides make you run off high octane gas. Maybe like 10 hp after hours and hours and hours of scanning/data collecting and numerous chips.
I'm kinda taking a break from data collecting because of the lower temps. I'm not trying to be tuned for the winter and get all kinds of kr in the warmer summer months.