Um, I think there's a write up on se-r.net. You don't want your front tire pressures so low that they roll over onto the sidewall. Usually run like 33-35 fronts on the street and 33-35 rear. For the street, I'd say there's not much you can do to affect handling with tire pressures(while being safe).
At an auto-x, I generally have the tires at 38-40 in the front cold to make sure they don't roll over. The rears, I'll set really low at like 28 to make them roll over because once they roll onto their side wall, they'll slide. I had tried increasing the pressure really high but that didn't do anything for me to reduce understeer. On a racetrack though, I think I put my tire pressures just a couple psi higher than my street setup.
I'd say go to an auto-x, and play around with your rear tire pressures and see what happens.