Any ideas? Rattling noise at idle, vid inside....

SO, I'm having trouble with this noise, it is not present on cold starts, its rpm dependent, goes away if I rev past 900rpm , and seems to be loudest on the passenger side of the engine when listening with the hood open, and from the back of the engine when listening from underneath the car.

I thought it was the heat shields, but it doesn't seem to be coming from that low, especially when I'm under the car.

Its a metallic buzzing/higher frequency rattle you can hear in the vid:

http://youtu.be/wATBNYFkw0I


Not sure what to make of it, maybe a pulley?

I have noise very similar to this that I only hear between 3500 and 4000 RPM. I was thinking possibly CAT starting to fall apart inside? But I don't know...

I thought a heat shield too, but I can't find anything, and it doesn't quite sound like a shield rattling.

My only other thought was something related to the intake, but that doesn't seem right either haha

Hopefully one of us has luck in determining what it is!

Ended up being the tensioner pulley for the timing belt.