I can't remember exactly what the belt drives, i think its just as you have suggested.
Its been at a diesel specialist for 3 weeks and they are stumped.
We know the pressue regulator on the hp pump is going out of range but cant find out why it is doing this? Their last suggestion is to have the injectors out and test them but i can't see there being a problem found?
The ac compressor making it worse is just bizarre