It has been doing this a while. Not a click or knock, but like a tsk sound, Sounds like maybe a clutch to me? It increases its rpms as the car does. Comming from under the car, right behind the wheels... post a vid up 2morrow. (car runs perfect and does miss or burn oil at all) thinkin it could be a clutch??

 

mine made a noise similar to to what you're describing, it went away when i replaced the serpentine belt.

 

yeah that would be nice if that was it! ill go ahead and change it, it makes a squeal noise when I take off but everyone is tellin me its my intake rubbing? only in low rpms. Might as well change the belt and see how that does!