The best way to work out where your tyre pressure is and where it should be is to look at your tyres when they come off the car, this will give you and indication of how your set up is also.
Try to set the pressure's cold, do some runs, check the hot pressures and then look at the tyre, it should show even wear across the whole tyre, too much in the centre = too high pressure.
Don't be afraid of low pressures, at Eastern Creek turn 4-12 circuit at night we start at 29 degrees and work down from there.
Hope this helps and...
Stay Sidewayz Kidz!