I am losing power / rpm when going uphill. It is fine on flat or downhill situations. Strangely, I’d the PTO is engaged (ex: bushog),the power does not drop. The rpms/power drop when I press the pedal. As soon as I lift my foot off, the rpms jump back to normal. I’ve recently changed fuel filter, oil filter, changed out all hydraulic fluid and replaced that filter, replaced air filters. The two things that I am thinking are: 1. Something is blocking fuel intake inside tank (hence the power drop uphill) or 2. The fuel pump is struggling. Any thoughts? How can I test the fuel pump integrity? Why is it fine uphill when the PTO is on?