Buzzing/razzing sound from the passenger side of the engine?
5.4L 2002 E350. It started awhile back, maybe November. I also noticed a drop in performance - about 2-3 MPG drop. I took off the inside covers and started it up so I could get a better bearing of where is is coming from and it's near the top of the engine, around the valve cover. You can only hear the nose when it idles, press the gas and it's either overcome by the other noises or perhaps it stops.
To me, it sounds almost exactly like the sound I hear from my '91 Dodge 3.3L's PCV valve which seems to have gone bad.
Thanks in advance!