[tblake]

Pull #2 plug out and take a look at it. What color is it?

When you say you rev it and the temp goes down, makes me think there is air getting in the system.

Are you sure the coolant isn't leaking out? What does the underside of the oil cap look like? Slimy sludge on it?

Take a look down under your throttle body and on the other side between the power steering pump and the LIM. Any seepage?

When your car is cold and you start it, does the radiator hose get hard immediatly on start up?

You could also have a shop do a leakdown test on your cylinders and listen for air bubbles escaping from your radiator.