Unless you are going to extremes on temp, I would pay no attention. Temps will typically rise enough to make somwhere around 8 PSI from cold to after driving a few hours. I generally start with 10 PSI below the max rating when cold and go from there.
Looking at your mods, I am curious what tires you are running?
I've got yokahama advan sports in the back, 285/45 (it may have only been 40 aspect) on 18x10 wheels.
Goodyear Eagle F1 Asymmetric in the front.
I seem to have good enough steering response, haven't had any issues with understeer.
Not exactly convinced the rears are all that great though. I expect some lost traction at lower speeds, but the other day, I laid some serious rubber at between 70-80. I was wondering if it was cool weather... but I think I may have the tire pressure a bit high (35psi), and lowering it should help?
I run my R888's at about 36 PSI at cold temps. They get up to about 40~41 on DD duties and are happy with them. They will not hold as well on really cold roads or until they get warmed up. Unless you are having this problem consistantly, I would not mess with pressure that has been good until this point.