2005 Honda Accord Center Dashboard "Squeak"

My 2005 Accord 4cyl auto trans. Has developed a very annoying high pitched squeak that seems to be emanating from somewhere in the center of the dash only when the trans. Shifts from 2nd to 3rd gear @ about 2000-2500rpm. The dealer replaced the belt tension pulley, serpentine belt, and a gasket connecting the exhaust pipe to the cat. Conv. To no avail. Allegedly, all vacuum lines/connections, driveshaft heat shield have been checked.I placed a stethescope over the center vents and the the noise seems to originate from that area. This is NOT a temp. Sensitive condition. The a/c blower motor has been ruled out. Trans. Just serviced. Any ideas. It's driving me nuts!