Feb 9, 2012 (7 years ago)
Check your EGR,it's down under the rear of the inlet manifold,you should hear a bzztd when key on engine off,no buzz then the EGR spindle is siezed,and if it's siezed in the open position the the riser pipe from the EGR to the back of the inlet manifold will be warm/hot when running.
I cheat when I test it,I fit a blanking plate in the EGR to manifold flange,temporary only!
If smoke and running problems dissapear it's confirmed,not cheap though,around £500 + the dreaded if I remember right.
Nissan consult is a must though,the injector pumps are not the cheapest to overhaull,better to be certain!
And don't remove the inj/pump without locking the idler gear,it kind of resets itself and then you cant reuse it,another £200+