Searching is ur friend. It will only void your warranty IF they can prove that the aftermarket part caused the problem. Some dealerships will refuse to work on your car with certain mods, CAI's being the main culprit.
I took my car to the dealership w\ short shifter and exhaust and they did not say anything about it. (p5 going through warranty issues) so they WERE looking at the car for certain problems, and said nothing about the mods I had done.
