my understanding is that it's largely academic. people who mod their cars tend to do so in a way that could conceivably affect many expensive parts of the car.

my understanding is that it's largely academic. people who mod their cars tend to do so in a way that could conceivably affect many expensive parts of the car. AFAIK, the most common mods are to increase peak output of the engine, change the power curve of the engine, or to change the exhaust sound (which also affects the engine and usually requires a tune). anything that changes the behavior of the engine can be reasonably argued to contribute to failures in any part of the drivetrain. I'd guess you're right in general though. if the dealer wants to argue that they don't have to fix your power window because you're running an aftermarket exhaust, they're in the wrong, but it's probably not worth taking them to court.