As Shaun stated, I would make sure the dealer is aware that they sold you a Tuned car so if any warranty issue, they will have to stand by it being that you signed paperwork assuming the remainder of the factory bumper to bumper. If you do not have this noted, they can claim you made the alterations to the tune causing any failure. That said, if you flash a new tune in the car it would be post sale and could possibly be determined.