I've seen this with many cars in my life (none of them my own I must add), nine times out of ten it's down to the breaking in the brake pads not being done right. In fact every case of "warped brake disc" that I have been confronted with has turned out to be friction pad material transferred unevenly to the surface of the disc. This uneven deposition results in thickness variation or run-out due to hot spotting that occurred at elevated temperatures. If both disc and pad are not properly broken in, material transfer between the two materials can take place in a random fashion - resulting is uneven deposits and vibration under braking. Similarly, even if the brakes are properly broken, if, when they are very hot or following a single long stop from high speed, the brakes are kept applied after the vehicle comes to a complete stop it is possible to leave a telltale deposit behind that looks like the outline of a pad adding to the unevenness of the deposits. There is only one way to prevent this sort of thing: following proper break in procedures for both pad and disc and use the correct pad for your driving style and conditions. All high performance aftermarket discs and pads should come with both installation and break in instructions. The procedures are very similar between manufacturers. With respect to the pads, the bonding resins must be burned off relatively slowly to avoid both fade and uneven deposits. The procedure is several stops of increasing severity with a brief cooling period between them. After the last stop, the system should be allowed to cool to ambient temperature. Typically, a series of ten increasingly hard stops from 60mph to 5 mph with normal acceleration in between should get the job done for a high performance street pad. During pad or disc break in, do not come to a complete stop, so plan where and when you do this procedure with care and concern for yourself and the safety of others. If you do come to a complete stop before the break in process is completed there is the chance for non-uniform pad material transfer or pad imprinting to take place and the results will be what the whole process is trying to avoid. So in short: do a proper break in of your pads and discs and do not keep the brakes applied after hard braking!