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.
Audi R8 V10, 6MT, Ibis White/Black with Red Contrast Stitching
Z4 sDrive35i, 7DCT, Alpine White/Coral Red [Retired]
335i Coupe, 6MT, Space Grey/Coral Red [Retired]