Here is a video, it sounds worse than it is. Unfortunately i thought i took a better video, but must have pressed the stop button.

The car is supercharged with aftermarket bolt on's, the noise *appears* to be coming from the rear.

I have had a look underneath the car and i can't see any leaks, exhausts rattling or much else odd.

Kind of sounds like a subaru exhaust.

Any ideas?

http://imageshack.us/clip/my-videos/717/mg1.mp4/

 

your link doesnt work

 

Thanks, sorted the link.