i bought an extended warrany through MAPS for my 03 Mach. the only thing i've done is install a steeda short throw and a C&L mass air. thinking about putting in an x-pipe. if anyone has any experience with MAPS and getting hassled, let me know.
Unless they can show your aftermarket part directly contributed to whatever engine failure you had, they can't revoke your warranty. The couple times I've taken my Mach into the dealership for work, they commented that my modifications will void my warranty. Bullshiite. They just say that to scare you. I'm not shaking, but my Mach is.
Actually anything you change on your vehicle after you purchase it , they can say "voids" your warranty. Best answer is keep all your old parts and re-install if you have to bring it back. But a chip or tune you can do and bring the factory settings right back. A chip like JET you can take out. A tune with say a diablo you can do and undo.
most dealerships wont cause its a customer paid deal but if the rear end got screwed due to teh install then yes but there is a time limit like 3 months or so............