GM rotors 'warp' because of 2 things. lugs not torqued properly (in sequence to 100ft/lbs) and 'power brakers'
people who slam on the brakes and keep there foot on the brakes when stopped. The pads heat up rapidly and then transfer the heat to one spot. The proper way to brake is to stop a little short of where you want to be, then let the tires roll a bit to spread the heat out. And stopping smoothly instead of panic stops helps too. since I have been doing that, no pulsating brakes!