Man, its tough in this area, better off with a mail tune and data logging it. There's speed factory in el.paso but I wouldn't let them tune my car. They seem to deal with mainly fart cans.
i know speed factory handled a 600+ GTO but other than that its all imports. there is also HP performance in roswell. ive been by there shop and they seem legit but i have no personal expierence with them. HP uses diablo only so if you use SCT your kinda screwed. there is dyno edge in ABQ and motiva also