thanks, i've plumbed in a fuel pressure regulator before the fuel rail which enabled the problem to be diagnosed. I've taken the vaccum pipe off the manifold and connected up to a bike pump. Pumping on this showed that up to around 7 bar at idle. Does this confirm that regulator upper diaphram is ok? How can i check vaccum pressure? i have a boost gauge plumbed in to another port on inlet manifold which should relect the pressure going to the fuel regulator shouldn't it (providing vaccum pipe not leaking)?