The pressure for your lift valve and tilt valve are one in the same. Your main pressure relief for these two is usually right above the input for the hyd fluid. The other valves that have adjusters are for each function that needs to be reduced from the high pressure.

I just had one of my mechanics in the field with the same problem on the same Nissan I believe and I just had him adjust the timing to give it a little more power and to lean it a little. It worked for him, sometimes it is a worn engine without compression but most of the time it is cured by adjustment. 2300lb hyd pressure is fine and is not the problem. Check the pot as Mr Fixit stated if it has a kick otherwise clean and adjust the carb or time. Good Luck