I've just noticed this problem pop up today, I started up my car and let it idle for a few minutes and then hit the accelerator and let it rev to about 3000rpms for a second then noticed a nasty rattle that I could hear coming through the shifter hole. I peeked into the engine bay and couldn't really hear anything but then went under the passenger side of the car and could hear it quite distinctly. If it means anything, the primary (or secondary?) fan now runs even when I turn the key to just turn on the accessory. Anyone know what this could be? here's a video, sorry for the sub-par audio quality.

 

Something sounds angry, and holy cow 2200rpm idle? Um well check the exhaust system for loose tin heat shields, check for big hole in exhaust. Which fan, left/right.

 

the cat honeycomb broke

 

really? I've never heard a cat sound like that

 

After doing some research I think it's definitely a broken cat, it's coming right from it, looks like I'll just order a new one. Any suggestions on which one to buy? it's a stock exhaust if that helps