The existence of aftermarket parts does not automatically void your warranty. They must prove that the failure of a part is caused by or related to the aftermarket part to deny you warranty. Of course, you may have to get a lawyer involved at that point if they try to screw you.
E89 Z4 sDrive35i 7DCT "Zayna", Alpine White/Coral Red
E92 335i 6MT "Calixta", Space Grey/Coral Red [Retired]