Hi Martin,
Your fault code listed is; P0380 Ford Glow Plug/Heater Circuit A.

This code may cause the system to run in a LOS, but should not cause a intermittent loss of power/limp home.

I would not check the Glow plugs by removing and bench testing,(some of them do not work off 12volts any more)
A quicker safer way may be to use an Amps clamp. and perhaps a volt drop test between Batt+ and the glow plugs.

You say the readings looked good, but what actual were the readings.

What is the supply line reading?

What is the duty cycle of the control circuit for the high pressure pump?

What is the history of the vehicle?

What is the fuel like?

Regards Mark