[V8] Vacuum piping

[pdlord@talent.com.au]

Can anyone tell me where the left port of four on the lower front heater box (ie
for lower vents, at the 'back' end of heater box when sitting in the car) goes?
There is nothing connected to it on my car. Is this normal, or has someone
ripped it out? There is is a red vacuum tube not leading anywhere on the
driver's side transmission tunnel .

I can't seem to find a vacuum diagram for this in my manual. Any sugestions?