Hi Mark, just read about your problem, had a problem like this on a 03 fiesta 1.4 tdci a year ago, ok on flat lacked power on hills & could stall car if not enough revs given. Found problen with Camshaft as cam lobs are pressed onto the shaft & set at correct angles to open valves at correct times, the problem cames when the lobs move then altering the valve liftcauseing the lack of power under load. I fitted a new camshaft & full power was regained. I hope this helps.

Martin