Brian,

Been a while since I layed hands on a Cedric.  Working from memory so
forgive me any errors.

ECU was either behind dash on floor centre (tunnel area or behind the NS
kick panel (footwell area).  Self diagnosis conducted by turning a screw (on
ECU) all the way (CW/ACW can't remember) to the end which kicked in the
flash code reader and gave a serious of flash codes.

If one LED is shown then a long flash = 10 and quick blinks = units.  5 long
and 5 short flashes therefore = 55 and was the no fault found code.  Cannot
recall all the others.  Please try ther Nissan dealer again for a manual as
I was sure these were available all be the cost is around ?50.

These types of faults are never easier on older cars as older mechanics with
history of these vehicles are rare.  Plus cars with donor parts (for
elimination) don't regularly visit the workshop.

One thing I would sugest eliminating - the Air flow meter.  Simply unplug it
and then start the engine as this will allow the vehicle to run from
pre-programed data (fail safe mode, allthough it will not rev above 2500 RPM
I think).

Apart from that the fuel pressure regulator may be jaming the flow of fuel
if the diaphragm is rupturted.

That's all I can add

Tony