0% your warranty can never be voided. (U.S.A) If you went in for a warranty claim on X part failing, Toyota would then have to have a valid case and prove that modifications contributed to part Xs failure. Obviously for things like a failure anywhere in the powertrain or drivetrain things like a tune can be sited as the cause 100% of the time because the car is no longer in the "as delivered configuration". If your steering wheel breaks obviously that claim cannot be denied because you have an aftermarket exhaust. Moral of the story if something breaks, do yourself a favor and return all associated parts to OEM.