they can only not warranty aftermarket parts you put on, stock parts you alter or parts that they can prove failed as a result of your modifications.
in other words, if you add an aftermarket power-adder they cant refuse to fix a bad power-steering pump, door pull, leaky roof, etc.
but, that leaves big-ticket items like the tranny, internal engine componenets and rear end. so there is risk. :smile
oh yeah, and a lot of dealers are begining to refuse to warranty bad MAF sensors due to KN-type oil/gauze filters being over oiled. so be careful!
__________________
Coming Soon: The Solstice With The Mostice