I used to run about 36psi all around on the stock tyres, but I never really experimented with them to find the ideal pressure. I'd suggest trying something like 38psi front, 36pi rear and give the car a good run to see if you like the changes. Basically if you're rear end keeps sliding around try dropping the rear pressure a little, and if you are getting lots of wheelspin you could try dropping the pressure of the fronts to find the balance you like between acceleration traction and cornering. Obviously you will need to wait for a while between changing tyre pressures to ensure the tyres are cold (a few hours or overnight for instance).