I've added (Speerzie) because I noticed he had a similar issue on bfuk but it was never solved by the looks of things.
So, my car is a Vanos 325i and it's making a buzz/rattle/rasp when you lift off from higher revs; 3k or higher roughly. The noise only lasts a second and then goes away but it sounds like chain slap/lash.
What gets me is that I've recently re-built the vanos with a new upper tensioner AND I've fitted the uprated tensioner. Actually, I replaced the spring in my older style tensioner which didn't help and then I fitted the uprated one.
I really can't see what else it could be tbh When I did the vanos I had a snoop around the guides looked fine as far as I could see as did the chain. I've heard on some forums (mainly American) that the oil pumps can become weak and can't cope as well as they did with the drop in pressure as the revs die down.
Any input appreciated guys