[ROVERNET - UK] SD1 Vitesse/EFI: which fuel pressure regulator (standard/adjustable)?

[pj.info]

Dear Rovernetters

I noticed that the membrane of my pressure regulator lets air passing through 
from the fuel supply / tank return side to the manifold depression pipe side. 
Is this normal? I suspect the regulator being defective. (I already had 
several cold start problems -just unwilling to fire up- although the battery 
was in perfect condition and the distributor / spark plug cables ok and fuel 
flowing though the rails by slightly depressing the flap of the air-flow 
meter).

Having had a look at Rimmers,  there are 2 possible choices for the fuel 
pressure regulator:
- Standard	ERR268 (now replaced by EAC1284P)
- Adjustable	EAC1284UR

=> Does the adjustable regulator fit just in place of the standard one?
=> Does anybody have had any experience with adjustable pressure regulators, 
i.e. how would you tune it (could this have an influence on the pollution 
figures NOx,CO,...)?

Thank you for your advice.

Best regards,
Pierre.
'86 SD1 - Vitesse