What does this vacuum hose connect to?

[Crimson Thunder]

I'm trying to get my wiper door to work and my PO had this line going behind the distributor and connected to the yellow hose that is supposed to go to the wiper door relay. I'm pretty sure the hose connects to the HVAC system under the dash. The AIM is hard to follow because it shows the 69 wiper door hose routing and not the 70 with the relay on the firewall. The hose comes out of the firewall about two inches below the limit switch. I'm holding the hose straight up for the picture(it has the clamp on it). I have a couple of vacuum diagrams but I can't seem to find out where this hose goes.

 

[bill81vette]

Have you been able to follow it and see where it goes???

 

[Crimson Thunder]

Without taking the dash apart. I "think" the hose goes behind the center gauges and to a round vacuum canister under the radio that is used for the ventilation control panel.