We would not be able to speak for the other tuner, but that is correct one of the benefits of using the AutoCal is being able to go back to factory settings when ever you need to. We have not had any warranty issues to date with our tuning.I don't know anything about tuning but I know that when I use my hypertech and or autocal I have the option to install the tuned file or put my stock file back, I know the stock file should always be kept for instances just like this. If he went in there and somehow edited some specific files maybe he forgot something or left traces behind. @BlackBearPerf