PSI for stretchyness

[AM E36]

205/40/17 all the way around. Falken 502A tire. 8 inch diameter in the front 9 in the rear. 1998.5 BMW M3 Coupe. 3175LBS.
About to take a roadtrip, I've been killing 3 hours at work trying to figure out how to calculate proper tire pressure. Anyone have any input?

[hinrichs]

i usually run around 38 or so in my tires or whatever my tire guy suggest, basically whatever the tire says usually works for me