I have a 2014 ZX4800. I've noticed lately that the mower is bogging down more than usual when cutting thicker\higher grass. I know this is normal when grass is overgrown and dense and you're cutting too much at once, but this mower is not performing like it did before. Ive replaced the deck belt thinking it was worn. Still same problem with sharp blades, new deck belt, throttle WFO. Could the pump drive belt be contributing to this power loss is any way? If not, what else could? Only other things i can think is sticky bearings or worn tensioner spring?