You are now the third person (sorry fourth) that has had a problem very close to Duggan, Me (a31ford) and another guy(can't remember his name).
Engine boggs about 2500, gutless wonder, won't climb a hill, etc, etc, etc, It'a a random thing, sometimes pushing the clutch in and reving it fixes the problem, but only for a bit.
The following fixed 3 for 3 people... tank sock (on the fuel pump tube IN the fuel tank). AND, replacing the TPS sensor (on the side of the air horn, and throttle).
You will note that a short lived fix, is to "code it", and clear the codes" (KOER, and clear) restart and drive, problem is gone for about 10 minutes or so.
The TPS is the main culprit (IMO), and the sock causes the "motorboating" that is in the power loss.
As for the Code..... (see below)
Check the wiring harness on the DR inner fender (the group of 3 connectors, find the one that goes to the tank, look at the ground connection (big wire in connector) IMSC it's a white wire, BUT not sure.
Greg