I am writing this because I struggled to find good current information:
2008 Chevy Tahoe 5.3 flex fuel 4x4 3.73 gear ratio. (Completely stock)
Objective was to have better drivability and towing capabilities.
Tune provided by Wait for me performance Cost $125.00
The following improvements
No more Active fuel management 8 to 4 cylinder shut down
Much better acceleration and improved shift points
Idles super smooth.
No speed limiter (will never find out)
Tows 5,000 + pound trailers much better.
Gas mileage ( can not conform better also can not say it doesn't )
What I haven't liked: Nothing
I hope this helps.
Is that the guy in Warsaw?
Did you meet up with him or mailorder?
I emailed him about an LS1 tune and he seemed to be decent to communicate with, but found mixed reviews online and most were older.