this is based on my own experience and some info from a Lombardini agent.Turn the camshaft untill the injector is off the cam then unscrew it until the screw is loose then by hand screw it down until it touches the plunger then using a screwdriver screw it in another 1 to 1 1/2 turns and tighten the nut.Check that on full cam you still have downward movement of the plunger it is important that it doesn't bottom out.Repeat on all the injectors.I have been told that you should have around 2 threads showing above the nut however I have tried some new injectors and they are showing more than 2 threads.Each half turn is around 5 degrees on the timing so I would start at 1 turn and go upwards in small adjustments.The other thing that might be the problem is the adjustor screws under the throttle.The top one is the slow speed(tickover)and the one underneath is the max.revs.There is not much adjustment on these so adjust in very small increments and once running turn down the max.revs until it will do about 65mph.These engines are a nightmare and no one has a good word for them.Indeed I might even get rid of my pickup and look for a petrol.Hope this helps but you do this at your own risk,regards,Alistair Gilbert