Kioti Power Loss Continued...

[Midniteoyl]

There's also a PTO driven pump on that sprayer, no? That's what most here are pointing to.. You can run and drive just fine with no load, even with the PTO engaged because it takes very little of your HP to do so. You can also run the sprayer at a slightly reduced PTO RPM, and thus even less HP, with no apparent problems. This leaves something in the sprayer's pump as the most likely culprit.

Does it have a recirculation bypass?

The only other thing would be air/fuel, as in clogged filters, weak fuel pump, dirty injectors, etc.