I think you're looking at slightly the wrong thing. I think it's not the
air being exhausted out the doors, but rather the turbulence at the door
intersection with the front door jamb/ corner. What VW did on the 88's
was to COMPLETELY seal this gap flush right to the outer surface with
door gasket. I've had 6 of these and the 90 and 91 are  noticeably quieter.

Reinhard Vehring wrote:

>Regardless, it seems to make sense to block the noise
>from the door vents. Any suggestions? Just stuffing
>them shut may not be a good idea. Doors get pretty wet
>inside when it rains and I don't like rusted out
>doors. Dynamatting the door doesn't help, if it's the
>vent opening and not sound transmitted through the
>sheet metal. Maybe it's better to work on the panels?
>
>
>