How about an old B&G racing computer, some decent instruments and a log book.
Figure out ET/Air Density change ratio, throttle stop ratio, vapor pressure fudge factor, track, wind, clouds, watch everyone in front of you to see what they're doing, figure out how you want to race the guy in the other lane, and throw a number in it.
Worked pretty well.
If the results don't match the theory, change the theory.
