I purchased a used 2007 3540HST 1235 hours, was told it was an ex- USFS rig. Factory FEL and BH900 backhoe. The unit runs good and operates OK, but seems a little underpowered at times. Both FEL and backhoe leakdown, even while running. I thinking the main hydraulic pump seals are bad or worn out, I can't see that every hydraulic cylinder has bad seals. How would I go about testing the main pump and the cylinders? Any idea what a new complete hydraulic pump replacement would cost? Is there a main relief valve that could be bad? Thoughts would be appreciated.