The plastic cowl cover across the bottom of the windshield vibrates against the glass with a "Bronx Cheer" type noise. This is most pronounced between 40 and 50 mph due, I think, to air flow on a loose plastic cowl. It has progressed over the past few months from an occasional buzz to a more or less constant annoyance. I thought at first that the wipers were vibrating, but eliminated that by removing them.

Does anyone know how to tighten up the cowl? As far as I can see the cowl is held in place with a screw (quarter turn screws?) on each side, and then perhaps sealing tape securing the edge of the cowl to the frame in the engine compartment. Turning the end screws doesn't have any effect.