There is another guy that does some excellent GM tuning. Nelson Performance from San Antonio, Texas. Nelson Performance! Fill out the info form letting him know what you want to do and he will program a new PCM and ship it to you. Once you get the new PCM all you have to do is plug the new one in and ship your old one back to him and your done! No down time!
EDIT: This is the owner, Allen Nelson's website, LS1Truck.com Here is a post of an '07 with a 5.3 that he dyno tuned(he can do it if you can get your vehicle to San Antonio). His user name is farmtruc. http://www.ls1truck.com/forums/dynodata/20...v-5-3-dyno.html