Dave asked Is this a "feature" or a problem?
Feature.  VW changed about '88 and tied the old fresh air vents to the
heater.  When I went from an '85 to a '90 I ran into this, the duct to
the drivers side vent was loose under the dash, I got nothing.  There
are times in the summer I'd like to have the fresh air back, the amount
of air coming out of the vents in the '90 is very small compared.