Warranty technicalities are nice to read but the bottom line is a dealership has no obligation to service your vehicle. So the best way to view this is from the dealer's point of view, which is maximum profitability. That is to say what is more profitable for the dealer? To honor warranty coverage on a modded car or deny warranty coverage as per modifications notwithstanding root cause of the issue in question and make the customer eat the cost of repairs?
If you mod your vehicle in any way, I hope you know someone who works at the dealership.
