[sparkycuda]

Hydraulic pressure is a function of close-fit of pump internal parts (pump efficiency) and the resistance in the system. A good hydraulic pump will build pressure regardless of flow (volume) in the system. Increasing pump speed will increase volume of oil and therefore, speed of the actuators, but pressure is still determined by pump efficiency.
You might see a small increase in pressure with higher RPM but it will not be much, and as the pump wears, that pressure will drop off.
Have you adjusted the pressure relief valve to see if the pump can produce more pressure? That might give you some extra power, but have to watch for additional heat build-up in the system.

Ken