Originally Posted by The HACK

Okay, I think I know where the problem is. And you may be right initially, that the PADS are the problem.

The pulsing sensation you feel in the pedal wasn't from the ABS system. It's from the pads skipping across the surface of the rotor due to over-heating between the pads and the rotors. The pads "glazed," meaning heat near the melting temperature of the pad material allowed the brake dust to fill all the little surface imperfections and made it mirror like, and the result is instead of grabbing onto the rotor surface and providing friction to slow the car down, it just glides over the rotor and sort of just bounces, like trying to slide two pieces of mirror together.

The result is you'll feel an odd, almost ABS like vibration when the pads knock back into the caliper from the surface imperfections of the rotor, pedal is firm but car's not slowing down. Once the pads cool off and the brake dust that fill the nooks and crannies can no longer stick to the little nooks and crannies the brake works again.

Heat soaking into the fluid would result in a soft pedal, so I'm not sure if it's the cause here.

At least that's what I think happened. A more aggressive, track oriented pad will likely cure the issue.