Haha, I appreciate the post OCG35. First of all, there are TWO sounds. The whoosh is when the RPMS decline, which I have pretty much sorted out to be from the y-pipe (back pressure).

The OTHER sound (which I started this thread for) I mentioned sounded 'tinny', nothing else. Then it was mentioned that it might be rasp, which I decided to look into. After listening to it again on my way to work the other day, I described the sound to be that of rattling/vibration. So, that's what we're working with. I've been told that it might be the head shields from the HFC's, or to else check the entire exhaust to see if anything is loose that could be causing the rattling sound. But thanks for looking out.

`John

 

Thought that I would update my thread.

I already removed the y-pipe and it was still making the vibration sound, so I took the car back to the shop yesterday to have it checked out. The left HFC was literally 1-2mm away from the heatshield, so the guy bent it as much as possible (which wasn't much), and the car is now sound free! Fixing that has made me SO happy I can't even explain. Thanks again for everyone's help.

`John

 

Well, I just installed resonated tp's on my coupe today and I am getting the same issue ( the swoosh sound only). I was able to check it out while I had the car jacked up and it's definitely coming from the y-pipe. I say it sounds like a rattlesnake when I decelerate from a high rev and stopped. The Y pipe also shakes itself as it gets this back pressure sound. Is this normal? Should I consider getting aftermarket y-pipe?