At idle my 2012 Mini Cooper S doesn't seem to make anymore noise then the lifter tick but between 1200 and 1800rpm if you try to accelerate there's a audible rattling sound, also does it if you rev it. If the engines going a constant rate it doesn't make the sound, only when its accelerating does it make it. Anybody know what it could be?

 

Probably best to record and upload a video or sound clip.