Hi guys, the problem turned out to be the timing chain slipped a tooth. the chains rarely snap on these according to bmw just stretch. this along with the fact that the tensioners and guides are made of nylon and wear down, and the lifters are hydraulic and move up or down when the car starts or stops to create tension, apparently when the car stopped they dropped as they should but when started again they did not lift and create enough tension causing the chain to slip a tooth. when I asked how this did not do any damage to valves etc. I was told that there is a difference between cars with belts and chains as if it was a belt then it would go BANG, but this set up on the beemer just cause the chain to spin without affecting the rest.....thank god. anyway £800 pound later :( and new timing chain, lifters, tensioners and guides and labour ..its now running sweet as a nut, seems to be quieter, smoother, better throttle response and more responsive :D. right for a few years now lol.