Needle valve is a top quality Tognella one, bought from Dependable. Patrol is a 2013 CRD, so that vac tank shouldn't be the issue. Based upon the fact that this just happened out of the blue after a year of running fine, I am inclined to go with the faulty MAF sensor suggestions. Does anyone know how much a new MAF is going to set me back? The Patrol is still under warranty, so if I put the boost back to vacuum/ECU control and take it to Nissan would they be able to diagnose the faulty MAF? Thanks heaps for all the suggestions!