[gbeeley]

If it is coming from both valve covers, especially if it started over a very short period of time, I'd suspect something systemic. I have heard that the gauge on the dash isn't a super-reliable way to check the oil pressure, but not sure to what degree....

I'm not entirely sure if it could cause the noise (crank pressure would have to get awfully high), but you might check your PCV valve - to check place a piece of saran wrap over the oil filler opening (cap off) with the engine at idle; there should be a slight amount of vacuum drawing the plastic wrap in (don't let it actually go in there!). PCV valve on this engine is a PAIN to replace - because it is wedged so tightly in there....

Other than that the only thing that I can think of is low oil pressure at the lifters. Maybe someone else here can shed some light on it...