I'm ALWAYS amazed at just how many of these threads pop up .....
The GM saw the OCC and denied saying the car has a tune?? Do you know how ridiculous that is AND the fact that having an OCC does NOT translate to having a tune? OCC are specifically designed to work in conjunction with turbo vehicles ... period.
Absolutely ridiculous ....... take a look at my garage and the list of modifications I have made to the car. Not once have I ever been denied warranty service/work because anything was in place on the car. This with the car having been in to 2 separate dealerships.