I have a hypertech tuner that I am using on my 2008 Duramax 2500 H.D. Chevy. I don't pull anything and its my first pleasure truck. If any of you use the hypertech can you tell me where you get the best mileage. Stage 1,2,or 3. I cannot get over 15mpg no matter what I do. I put a k + n air filter in, but still no luck.