Well technically under the Magnuson-Moss Warranty Act you can modify your car all you want as long as the modifications are legal, which a cold air intake would be, and the dealership cannot deny you coverage. But as Truth said about denying coverage, they will do everything they can to blame it on the modification and deny you coverage, but they technically can't unless that part caused the problem. So having your radio all the sudden never work they can't be like yeah that cold air intake of yours makes your warrenty void and is what caused your radio to crap out. They have to prove beyond a reasonable doubt that the modification caused the problem to deny coverage.