Mr Medlock has spent the morning removing the cam sensor but the replacement will not be here until tomorrow. ( a real sod to unplug, especially if you have done the manifold swop). As I mentioned earlier, the noise and vibration is loudest at the fuel rail. This seems to be quite a common problem on M52s although various solutions are put forward like changing oil, adding additives etc etc but a couple have cured the problem by replacing the sensor - the theory being that with a faulty sensor, the injectors don't know when to squirt. Anyway, we'll see in due course. I've ordered a Meyle sensor but some have said that the system only really likes Siemens!