What is this sound!!

[diettmannd]

Background 2008 fsi with a lot of miles. 206k lol. Has a strange sound on deceleration. Can't really tell when driving but very apparent with a rev in neutral. Car actually runs decent. Completely stock, this sound is only apparent behind the motor can not be heard from the under the hood. Sound stops after 1500 rpm. Just bought this car for dirt cheap and I mean dirt cheap. Has a mis on cylinder two from coils. I've had plenty of BMWs so I know all about stupid coil misfires haha. Any ideas?

 

[diettmannd]

Spools fine as far as I can tell and doesn't smoke like a blown turbo nor does it sound like one but it being that the sound stops after 1500 rpms makes be wanna say it's boost related but I don't know these cars too well.

 

[3BallUG]

Sounds sorta like an exhaust leak. If its spooling fine and no dentist drill sound or smoke out the back cant see it being the turbo.