i notice a lot of ppl talkin bout there warinties bein denied because of afftermarket parts, since i to enjoy boltin on random stuff, i felt the need to look into it, there are a lot of helpfull websites out there, from what i gather is basicly that if they deny you based on an afftermarket part you put on they basicly have to prove that said part is the cause of the failure, pretty much most ppl dont purse denied claims so they get away with it.
i found this site simplyfys it the best , i dont know about you but i paid 3200 for my warenty an i will be damed if they ever deny me cause i took my muffler out or put a new intake on, but at the same time if i throw new injectors in an they do find those to be at fault i dont expect them to replace what i put in, i hope this link helps out.
RPM Outlets Aftermarket vs. Factory Warranty (281) 261-6244