I've used them before and although they do what they say they do, you are literally wasting your money in my opinion. if you have access to a shop with a dyno and tuning programs, it is a much better way to go than a programmer. the shop can take that same $350 that youre going to spend on the programmer (which gives you a generalized tune built by hypertech or whoever the product is make by) and do a vehicle specific tune for YOUR truck. You can get the same speedo recalibration and all that stuff with a far better tune for the same money you would be spending. It's a much better way to go IMO. But on the other hand if you dont have access to a shop with that equipment then a programmer is a decent second best.