I do not have experience with your machine however increasing the pressure may not increase the speed. In fact I almost guarantee the pressure will not affect the speed. You need to look at the hydraulic system and find out if there is flow control somewhere. The flow control may be affected by a change in pressure but again you really need to look at the system.

There may be an adjustable flow control or a fixed orifice controlling the speed of actuation or if the flow or the system is at maximum you may have to increase your pump size. You will have to find the flow limiter feeding your actuator.