There's no speed up or down to change. The pump motor turns on full rpm when selected. Slow hydraulics is either oil filled with air bubbles or a bad pump. Need pressure taken to see what's changed. Also the pump splines to motor splines condition. Again if the pump is on and good battery, the slow hydraulic issue was present before the replacement.
Check also voltage configuration of pump motor. Most are 36/48v. Could be a odd one and wrong voltage.
Do you know if it has a pump chopper also ? Very few of these come out and blessed the market !