When I had mine it was full factory warranty extension for an extra 3 years, no limits or exeptions for, I think, 1500 dollars.
23.8 litres is terrible fuel consumption... sounds awful like boost issues to me.
Buy a Scangauge, best $200 you'll ever spend on a CRD.
While ever the engine is factory you don't need an EGT gauge but they are handy.
Neither of those will have any warranty issues and on the Scangauge anything like excess fuel use, high temps, boost pressure etc leaps out at you.
I had to adjust my turbo myself because the car was heavily modified, chips, exhaust, EGR etc.
Nissan would have a Cow if they knew
Yours is factory so I strongly suggest you bludgeon Nissan over the head till they get it sorted.
The documents are known variously as the "ZD30 Reference Document", "Patrol Bible" or similar and are what you want.
It may take 25 posts before you can see them on here.
Bottom line is get a Scan gauge or equivalent and go from there
They are available on other sites but IMHO do the post count penance as this Forum is a very good one