Before replacing rams, have you checked the hydraulic pressure against the OEM spec? Many tractors ship with the pressure relief valve set @ 2500 PSI when the system is rated at 2800 or 3000 PSI. That might give you the extra ummph you need.
To check it, you would get a liquid filled gauge and a quick connect and connect them in place of one of the loader lines. You then bring the engine up to 2500 or so RPMs, put the lever against the stop and see how high the pressure goes, then compare it to the rated pressure from your shop manual (or call the dealership and ask what it should be).
Aaron Z