Federal law prohibits the dealer or the manufacturer to void your warranty when it comes to aftermarket parts. The act is called the Magnuson-Moss Warranty Act. See link below:
http://www.enjoythedrive.com/content/?id=8128
However, if you take it into the dealer for a warranty repair and they find that the aftermarket mod caused the problem then you're SOL. Regardless, they cannot void the entire warranty.
Thrasher CAI, DHP v1.0 PCM, SLP Headers,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 72mm TB,
TB spacer, MSD 8.5mm wires, Autolite 104s,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials