Hey everyone. Trying to sell my car and none of us can figure out where this noise is coming from. It's a 2005 with the 4 cylinder, 2.3 liter, roughly 93k on it. The car runs great, and no stalling problems. But when it just sits at idle there is an excessive noise that sounds like it's coming from the passenger side of the engine compartment, and every once in awhile the rpms raise/lower only about 200 rpms. And when you take off and speed up you can hear the same noise, just in a higher pitch. Almost like a loose pulley/warped belt sound or an air flow sound, but I can't figure it out. I sprayed some WD40 on the pulleys/belt and it didn't help, so it has me second guessing. Don't think the throttle body, IAC, or clogged air filter would cause this noise would it? Other thoughts could be a stuck EGR valve but I don't know about this sound.

Any ideas? Thanks!