Well, all I know is that I'm running stock sized tires and I've had my truck up to and over 100 a few times. In fact yesterday when this happened it hit 100 and certainly was still pulling hard and finally after about 5 seconds or so it hit the ceiling. I'm fairly certain that I've got a stock computer HOWEVER, the previous owner must have done something because there is a big sticker on my computer box that says "Diablosport" and picture of a Devil. I'm pretty sure it's stock though (or the existing chip is in stock mode?) cause I can't make smoke no matter how much I try. I've been meaning to pull it out sometime and look at it I just never have gotten around to it.