A leaking cylinder will reduce splitting force but will not cause the engine to bog down. The engine will bog when excessive pressure is reached. Excessive pressure can be caused by the bypass valve for the high volume section failing to open if you have a 2-stage pump or the relief valve fails to open in the control valve.
Pics of the pump, cylinder ,and control valve could help in figuring out the problem.
Pics of the pump, cylinder ,and control valve could help in figuring out the problem.