I'm hearing things

and I can't figure out what it is. It's a 99 VE 5spd with 140K miles. I know the ball joints are bad and my CV joints are on the way out(and I know what that sounds like). This sound is more like a rattling or chattering kind of sound. I have loosened and tightened all the exhaust heat shields, exhaust manifold, intake manifold, engine cover, and just about anything else that I could see that could be contributing to the noise. I have found that if I keep it at a certain RPM that it can get really loud(I don't know what RPM since I don't have a tach :( ) I am just looking for any suggestions on things to check. I don't want to just start tearing into it or replacing things until I find out what it is. I'll take it to get diagnosed by a mechanic as a last resort if I have to. There are no performance issues that have accompanied the new sound either. Thanks for your help!

E

try and listen to where it is directly coming from, i once had this squeaking sound to my car when i first bought and it turned out to be somewhere around my belts, just open the hood and try to listen to where its coming from, if it dont work then i suggest you bring it to a shop, i believe most only charge like $20 to diagnose whats wrong

one way to check it is to remove the belts to see if its the engine doin it or soemthing around it like a water pump, power sterring pump ect ect