Hi Russell, Mark, Russell you were closest with item 1. It wasn't the crank key though, the exaust cam pulley was loose and had closed up the roll pin/ damaged the slot in the pulley. It was only about 0.3mm on the pin and 0.3 on the slot but it all added up to about 6mm at the outside of the pulley or almost a tooth! I don't think I would have found it without deciding to take the head off, glad I never decided to play "wait and see" and gave it back. The clue was I had been getting a "cam signal bad" warning in live data even though there was no fault code, I just couldn't make out what it was trying to tell me. Thanks for all the ideas everyone. Shaun.