Technically - here's the deal, guys. They can void your warranty if your car is modified - it reads so right in your manual. You can fight it with the help of Mag-Moss or a good lemon law attorney, but that takes time and patience (and money, in some cases).
Just for reference, I've been an expert witness in over 6,300 lemon law and breach of warranty cases in the past 5 years, with over 3,000 of those being GM cases. You can say "it's not fair" all you want, but just understand that if you modify your ride, your take your chances on warranty denials.
warranty isnt shiz when they see your tires and say you "abused" your car that is why Gm will soon go out of business i give em 10 mabe 15 years then they will be done f*****'s. They will look for any excuse to say u screwed you warranty unless the know for a fact that is was on them, different story. you put in a aftermarket cd player and your alternator goes they will blame it on that even thoe you know a cd player will not do that! honda is one company that is laid about stuff like this toyota also
EVERY manufacturer has the same rules, but some service managers enforce the rules stronger than others, especially when a customer's attitude is involved. You go into the place acting like a jerk, there's a much better chance than you'll get slammed.
EVERY manufacturer also fights lemon law and breach of warranty suits tooth and nail - customer service, my ass. Of course, if they rolled over and played dead and treated a car buyback like a refund or return at Target or Wal-Mart, I'd be out of a very nice primary income source.