I am working on a S60XM that is only developing peak 1500psi then drops to 1100psi at the test port at the control valve. I have tried adjusting the inlet and the outlet pressure relief valves. With no change in pressure. I took the control & presssure valves apart, cleaned them up and replaced the seals. No change but the pressure will adjust from 0psi to 1500psi peak out then it is still dropping to 1100psi. The motor acts like it is still under a heavy load after the hydraulics are run to bypass. I am afraid that the pump is the culprit but am trying to avoid this expensive repair. Any Ideas the group may have would be very helpful.