This seemed to start 1700km into a 1900km journey. Seems to be coming from driver's side, rear of engine bay. It's a buzzing or rattling sort of noise, more a buzz I guess.

Thought it might have been a heatshield rattling loose but can't find the culprit. From underneath the car the noise seems to originate around the turbo and move through the heatshields towards the guard.

Noise is only there as revs fall after getting off the throttle. Car is MY94 WRX. Exhaust is stock. Any ideas?

http://www.youtube.com/watch?v=Zpsd0tb3AAU

http://www.youtube.com/watch?v=5StqStUmq9k