Austin, TX
I'd like to recommend Protech Performance. Austin were lacking an impact wrench and stripped the hex on my struts while installing my spring. I took it the next day to Protech and they installed the spring for me for $50 and had it out that same day. Word on the street is that they're very reliable and to me they were nothing but courteous.
They also have a body shop which I've personally seen do good quality work. I'm going to have my M5 spoiler painted there and my roommate with a VW GTI is getting is Oettinger kit painted and installed there this August. More to come about their bodyshop's work.
http://home.austin.rr.com/ptp/
808 McPhaul Rd.
Austin, TX 78758
Ph: (512) 834-8771
Fax: (512) 834-8772