i got my gryphon with the custom tunes and it is great.my truck has the 4.6L and i have 33" tires with 3.55 factory gearing. i have not drove with it a great deal so im sure it could change up a bit but i am getting a little better than 18 mpg most of the time. i was getting 15.5 with the evo on the performance tune and 16 on the stock level. power is a lot better than the evo as well. the custom tunes sure are great. and i am very pleased with my gryphon. a big thanks to bill and corey for thier time and efforts. and all the moderators who helped me out with all of my questions. once again thanks to all.