Not sure if this is Wastegate Blow off from valves, but definitely should not sound like this. This noise seemed to occur infrequent at the beginning but became more frequent as time went on. I have had the car about 2.5 months (now have 3900 miles) and this is one of the problems that I have. There appears to be no engine or power loss because of the noise but it has gotten louder and more frequent, especially with increasing temperatures outside. This noise also seems to become louder as the engine temperatures/fluids etc get warmer.

Car is currently at Mercedes service having other issue fixed as well as diagnosing this noise. I had recorded the sound with my iPhone (as requested) and is legitimately identifiable. Bunny ears were actually placed by the service foreman yesterday for a sound to be recorded and sent to Germany engineers. This seems to be a problem that some people may not notice unless they hear it from other owners describing the noise,...... but then some would. I am not the only one who has this issue.