This is a vaccuum line i think, and it goes to the climate control circuit. I had something to do with it when I pulled my dash out. I had to back track it to find out where it went because it came unstuck out of the joiner inside the dash.
Falcon S, MPFI, red, Resprayed with colour coded bumpers, motorvator extractors, walker hi-flow cat, 2 & 1/2 exhaust system, cold air intake using hi-flow K&N pod filter (heat sheilded), stage 3 crow cam with a vernier cam timing gear. Severly ported and polished EB 4.0L head, shimmed valve springs - compression ratio (9.5:1 +). Making 145rwkw!!