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.
2012 Audi R8 V10 6MT, Ibis White/Black with Red Contrast Stitching
2009 Z4 sDrive35i 7DCT, Alpine White/Coral Red [Retired]
2010 335i 6MT, Space Grey/Coral Red [Retired]