Sometime ago, I purchased a diablo preditor. I went this route as it allowed me direct control of my truck. Speed limiter,re-calibration for wheels, long term fuel trims, timing and the list goes on. The benefit was to be better mpg and overall drive-ability. Now I started with the 87 tune which really woke this 8.1l up, thought there could not be much of a difference with the 91/93 octane tune, but there was a huge difference. I then added a magnaflow muffler (12599) and thought what the hell, I'd heard a lot about a diablew tune from Lew so I went ahead and ordered my tune. With the diablo, I loaded my stock tune and customized 93 tune and sent it off along with a data run. Lew worked magic and I am speechless as to the difference in this truck. It feels light,crisp and will blow the crap out of most cars/truck on the road. I got a buddy to drive my 740il bmw next to me and we stayed neck to neck until about 120, when I decided to back off. If you are looking at the best value for money performance add on this is by far the most advanced as it also allows you to tweak. By the way....just because I am offering my input ...please don't accuse me of working for them. I am and will proudly recommend Lew. He goes by 06MonteSS on the diablo website too. Try him you will not be disappointed.