So I was under the hood of my T/A ('84 15th Ann. with a 350 Goodwrench) tightening a drivebelt I put on a few months ago, it felt a little loose and just wanted to make sure it was on nice. So I pull my air cleaner off to have a little extra room and I noticed what appeared to be a vaccuum line of some variety not connected. It went to a plastic t-shaped fitting that connected to another vaccuum line, both of which seeming to come down and connect to a fitting behind my carb on the intake manifold. There was nowhere else for it to go, so I simply plugged it in and assumed it was the correct spot. My question is, what could this line go to? I followed it and it connected to some sort of sensor on the driver's side of the firewall, about 2 or 3 inches away from the hinge and fender.

I took a picture and circled the line I'm confused with, anyone who may know, I'd appreciate it if they told me.

maybe for the hvac, some cars have it incorported in to wiring harness for the blower motor

I second the vote on hvac.

It's basic vacuum source for A/C & heater controls usually. Should be a line runs from there to the vacuum ball (if your car has one) - it's usually under the driver side headlight. The ball 'collects' vacuum to use when there's not enough normal vacuum(like just accellerating). There is usually a checkvalve inline, allowing vacuum to go to the vacuum ball, and to the heater controls, but not letting it escape back into the manifold.

I see- like I said, I followed the vaccuum line and it went to some sort of electrical connection on the firewall. I had never noticed this being disconnected, however I never use my a/c (don't have) or my heater (summer time. lol), so I never noticed anything wrong. Oh well, thank you for the information, guys! Greatly appreciate it.