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.