i have a 04 5.7 and when i got it i bought a hypertech 3 and loved it, though theres not much you can do with it, i put 37's on an my mpg went down to 11, i just recently got a bullydog gt it has a few more options and a big increase in mpg 18 average, but sometimes it doesnt feel as strong as it did with the hypertech, but i do like it, i looked at all the other too but decided to go with the bullydog.