Interesting, a friend upped his ISM from 450 to 500 and needed a new turbo plus some other parts to get it done. He also did a resonator too. He loves the difference. I did just the resonator on my ISM and the difference was pretty noticable. Sure it was only ten miles per hour faster on the hilks and more pickup due to a faster turbo spook up, but it was almost a mile a gallon better milage too. Upping the programming will have a effect and you heed to see what is is. Are you pumping in more fuel so your milage will go down cross the board? Questions abound.