A friend'* 00 SSEi had a similar noise. I found that pressing against the dash right up by the windshield a bit right of center quieted it down. If that'* the problem, my cheap, low tech solution was to cut a strip of rubber off an old wiper blade, fold it over, and stuff it between the dash and the windshield. Don't push it down too far, if you go this route, or it will push through.
If you look for it, you can see it but it is rather unobtrusive as it sort of blends in with the black trim on the bottom of the windshield.
Black 2000 SSEi, Silverstar Headlights, Angel Eyes fogs, 3rd brake light overlay, hi-flo cat, drilled 180 degree thermostat, Intense FWI, PCM, shift kit, and 3.4 Pulley. Solid front mount.