Ford transit 1998 turbo diesel red light

this sound like you fuel injector pump stop solenoid is faulty it has an elec wire attached to it that with ign turned on it opens (clicks ) then clicks off/closes the fuel supply to the pump so engine stops ok? however the seal on the valve may have parted from the operating piston valve on solenoid and although it is free to allow fuel enough for start and running will also restrict fuel flow for more revs resulting in power loss as you mention ? also when ign is turned off the valve will operate but seal being not attached to piston ? fuel can still flow/seep thro to f i p and allow engine to continue to run ? hope you understand ?? this solenoid valve is a screw in type normally on top of f i p with a single wire to energize it looks like a larger type of temp sender unit ?