I was certain that this was either brakes or suspension noise while I was driving because I could hear it echoing off of cars, buildings, etc... So, I am sitting there idling and I start to hear it so now I can rule out that it only occurs while driving. Doesn't matter, hot or cold engine. I also heard a faint whining noise for a few seconds but the cam didn't catch that. Anyone have any ideas? I think we can rule out drivetrain since it's not moving and doing it. It's getting annoying, but I am more worried about it being a cracked manifold or something even worse. Take a listen.