I have the same noise the dealer changed the vanos tensioners right before my warranty expired and this didn't fix the issue. I still have the noise only on the first start after the car sits for a while regardless if it is cold or not. I recall hearing this noise from the early days when I got the car in 2008. I noticed if I tap the brakes few times and press them for 30 seconds before starting the car I don't get the noise!!!!. I'm curious if someone found a fix for this. My car has 33k miles
Here is a thread on the same issue.
http://www.m3post.com/forums/showthread.php?t=412843