Thanks HTC, some good info. It goes back to an earlier post I wrote about a vibration noise I get on cold start up, usually when the air temp is cold. Its a bit of a boring story about a dispute with audi and I will write a quick post for those who want to read it and i'll explain it better in there in the next few days. But basically a valve got replaced by a specialist near to the oil cooler, possibly number 6 in your diagram, and during this dispute i described it as being in the oil cooler, not knowing much about cars! They sarcastically wrote back saying there wasn't one there. Just wanted to clarify this really (couldn't get hold of the specialist), and you have! Cheers.