Here's my two cents about the GMPP tune. My wife has a Redline and I have the GXP. Both cars were given the GMPP tune at ~2,000 miles. I now have almost 65,000 miles on mine and have, as far as I know, not had any problems related to the tune. Last compression checks were in the 135-150 range. Wife's redline has just over 50,000 miles and she had to have her engine replaces about 2,500 miles ago if I remember correctly. The piston rings/and lands were basically falling apart. GM never got back as to what they thought the problem was so I guess we will never really know. I drive my car much more aggressively than she does so I don't think that is a factor. We both have a Magnaflo catback exhaust so again same-same. When we lived in Florida we both used 93 ocane top tier gas. The one major difference we have since living in Las Vegas is I have added a couple of gallons of 100 octane race gas at each fillup, keeping my octane rating somewhere around 93-95. But again I drive my car much more aggressively and she only goes WOT once or twice a week.
Mine - '08 Brazen GXP. Trifecta tune, Magnaflow exhaust, DDM backbone and brace, rear Z0K sway bar, Eiback springs, debadged, 19" wheels.
Hers - '08 Bluestone Redline. GMPP tune, Magnaflow exhaust, DDM backbone, debadged (mostly). FOR SALE