Sorry for all the posts; as a new user I can't post a video until I've had 2 other posts. My car makes a weird buzzing/rattling noise when the RPMs are steady. When they're increasing or decreasing, the noise goes away. Iused a piece of hose to listen and it sounds like it's coming from the exhaust manifold, but I can't get any further than that. Any suggestions...?

http://www.youtube.com/watch?v=XQkxsG_jhn0

 

Sounds like a monster vacuum leak. Does it run good otherwise?

 

WTF!!! lol never heard that before, might be the heat shield between the exhaust and intake tapping/shaking.

 

I was going to suggest heat shield as well.

 

The car runs fine otherwise - no loping at idle or anything; although when the RPMs are coming down it makes a slight groaning noise for a second that I can also feel with my foot on the pedal. If you listen really close to the video you can hear it. If it were a vacuum problem I'd think it would idle badly, but perhaps I'm wrong and it is a vacuum-related problem...

 

You can hear the honking/groaning noise pretty well at the 21-22 second mark, and again at the 30-31 second mark.