I normally run my 1988 4/4 (on the same tyres) at about 20-22psi which seems to be about the optimum for me. I did accidentally left my tyres at 28 after a track session once, it was way too hard for day to day use.
You might also want to consider the front spings - I swapped overto rutherford spings with adjustable AVO shocks (available from Tim Ayres, and Mike Duncan) which transformed the car, I need to think about a rear upgrade at some point too!
Theres also the new set up that folks have been talking about, which could be a bigger improvement.
Welcome to the mogness
by the way
