As it turns out there was a combination of faults on the vehicle one was a partially broken wire on the cam sensor that brought up odd readings from time to time. The other was the egr valve sticking and also someone had drilled a hole in the throttle plate to get round a idle valve problem. It was one of them you wish you never had seen and in the end i aint even quite sure what caused the emmissions to drop back down to acceptable levels. I cleaned the throttle housing replaced the throttle plate and idle air control valve that had long since blocked and stuck cleaned up the egr valve repaired the wiring and the emmissions had dropped and whether it was one of these things or a combination i will never know. The owner of the vehicle turned out to be an enthusiastic amateur and had messed about with a lot of things and that didnt help either. Anyway thanks for the help people.