If that's the case, I'm at a loss.
I don't have any leaks, radiator is a few years old but flushed before winter storage, coolant is neon green, thermostat opens and closes properly, and on the street I run between 200º and 215º, but at Waterford Hills I was at nearly 250ºF at the end of one session. Oil temperature was at least 265ºF, measured at the bottom of the oil pan. I'd imagine that the water wetter I was running was the only thing that kept the coolant system from boiling over all over the track.
I still have A/C installed on the car. Could the condenser be hampering the cooling system that much?