Originally Posted by ChrisSlicks

My theory is that once you got the tires and brakes up to full operating temperature there was so much stopping force that the ABS computer didn't know what to do with it. It over-reacted and reduced braking force by pulsing the front ABS at a high rate. I think the ABS computer needs to be reprogrammed to account for the added grip. Adding more grip and/or bigger brakes may only make it worse. I think the stock calipers and rotors are probably fine. Brake ducting would probably be beneficial.