OK so I searched for this problem. I found another thread that stated this exact same problem but in never ended with a resolution. I think that was kind of funny because the OP complain he found a thread that never posted a resolution so he didnt know what to do. https://my350z.com/forum/brakes-and-...ake-pedal.html

Car: 04.5 350Z Enthusiust with 65,000 miles.
Mods: Slotted Rotors (belive they are StopTech but where on car when I bought it few years ago), newer HP Plus pads, Kenetix SSV manifold, Injen short ram, Fidanza 3.2 clutch, Nismo Flywheel, Full suspension.

Problem: Sunday I went to the AutoX. Temps where almost coldest of the year, mid 40's. The day was going great. First time out on my new Bridgestone RE-11s. First 4 morning runs went great. Then the afternoon, 1st run I was killing it. I was topping out 2nd, hit the rev limiter a couple time (on purpose, to prevent up shifting & down shifting for a split second) then coming up to last hard right to exit the course I stab the brakes but all I had was a hard pedal. May have been normal pedal travel but no real braking. Ruined the run. Next run went fine. 3rd and final afternoon run exact same thing happened! Let off, reapplied, let off, reapplied, let off, pressed hard as I could. Pulled hand brake to slow me down. Then they worked fine again. Havent notice anymore problems.