ECT shouldn't limit the power at all unless things are wrong and it goes into limp home mode. I wonder if this is the case?

I parcially blocked fuel filter can leave the engine revving fine under no load but restrict fuel flow enough to cause power loss and stalling under load. Depends how bad it is but that would be the next thing to replace and at 160,000 if its still on the original filter then it definately NEEDS replacing!