Hi,
Did you solve this? I bought a 2011 Q7 at the beginning of January and after a few weeks it developed a rattly/clacking noise when cold, which was directly related to engine rpm. As the car was only a couple of thousand miles of needing a service I decided to wait... (I drive ~200 miles per day)
Turned out to be a snapped bolt on one of the injector rails, ended up stopped on the side of the motorway with smoke pouring out from the front of the car! nearly had a car fire, so worth getting it checked if you haven't yet!
