Hey man, it all depends on what you want to do with the car. Do you want to make if fast or look good? Or both? How many miles are on it? If you are toward the end of your warrenty, go nuts. Most of the time, and I say MOST of the time, the aftermarket parts are better quality than the OEM stuff. If you are truly worried about warranty stuff, stick to simple bolt ons like wheels, intake, or stereo stuff. That way if you run into a problem, you can easily remove it before taking it to the dealer. I have run into the problem too where even if it is under warrenty, and you have aftermarket parts on it, they will charge you extra because they claim they have to do extra work in order to work around the parts. Talk to your dealer and ask his oppinion on it. Good luck!!