Anyone have their brake pedal go rock hard on hot days?

[LtNoogie]

I first noticed this on a hot day while autocrossing and thought it was brake fade.

I've since swapped in SS brake lines, a high performance set of rotors, and high performance pads. (this was done for the autox, not the hard brakes).
Now that summer is here, I'm getting the symptoms again. My mechanic filled the system with the ATE Super Blue brake fluid so I don't think the heat is affecting the fluid.

I'm sure that if I take the car in to the dealer, they'll blame these aftermarket parts so I'll go back to my mechanic.

Thanks in advanced.