i just installed an uppipe and a downpipe on my 03 wrx about 2 weeks ago and everything has been great until now. starting about 3-4 days ago i started to hear a strange sound coming from the engine bay. to describe the sound, the best i can do is to say when listening to it i picture the turbo heat shield not bolted down, just floppin around. it seems to be coming from the turbo area; a passenger in my car said he thought it sounded like it was coming from in front of him. i hear the sound when i go over rough areas of the road, pot holes, speed bumps, and the like, which makes me think it's something loose floppin around. however, i also hear the sound when backing up, and between shifts when i shift at higher rpm. it isn't the heat shield - i took that off and the sound remains. i've tugged at the uppipe and downpipe, but they don't seem to be loose, nor can i see anything that's loose. any suggestions?