lower mph at track??

[jonnyk]

I agree, that FP is quite high. I shoot for 32-34 psi with vacuum at idle, or around 38 without vacuum. You will make more power in cooler air, but less in humid air...so the two effects will cancel each other, but obviously one effect is likely to dominate the other. The only real way to compare is to keep very close records of temperature, humidity, and barometric pressure (and the altitude of the track you run at) of the times that you run, and then figure out density altitude corrected times, and compare those.