Left side panel covering tunnel (drivers side kick panel) - remove it.
And the hush panel below the dash/steering column.

Pod that has two vacuum hoses and is vertical right above gas pedal area.
Linkage comes out the top.

With car running and fan at full reach up in there and pull that linkage down
and close that flap. If your vacuum pod is broken like mine was than your
forceful dash air was blowing out the defroster vent. Like Hit Man X asked.

If you can pull it down and the dash starts to blow hard.....
then replace that pod.
No dash removal necessary.
Although I did this with a strange variety of tools and patience it was done without removing instrument cluster.
If I ever do it again I will remove the instrument cluster to get at the pod
connectors which face up.

Good Luck.

It worked for me and I now have a nice strong dash air flow.
I also took the time to remove the glovebox and reach into the center pod and
used a paper clip like wire (made from music/piano wire) to wire that center flap open.
This gives me a stronger flow out of center on vent setting and lets me control it with the control knobs on the vents.

__________________
80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250