There is no hard and fast rule about fuel pressure.
Many variables such as injector duty cycle, fuel pump pressures, fuel rail diameter, fuel filter conditions will play a part in diallling in the correct fuel pressure.
2 engines with similar mods and similar setups might have different fuel pressure requirements based on the air/fuel ratio reading.
However, I think the rule of thumb is to keep fuel pressure as high as possible (not to the extent of jamming the injector spintles and rupturing the fuel lines)
Fuel delivered under hi-pressure allows for better fuel to air atomization.