2014 Silverado LTZ. I initially bought the tuner to turn off the AFM system. But being able to some what customize some of my truck%X92s features, I%X92ve noticed a big difference in HP for the 91 performance tune. I really like being able to read and clear a code that comes and goes on the truck (P050D). Only disappointment is I%X92ve yet to notice any difference in gas mileage. I may try the 87 octane tune in a month or so. It takes all of 15 to set up. I do suggest updating software before using it.