It's behind the TBI, and the end I can see is connected to a small check valve that's connected to the intake via a rubber line. Not sure exactly what it's for. I have looked over many diagrams but can't find it. Any suggestions would be greatly appreciated.

 

transfercase maybe? if its a s10 they have a vacuum source that runs back to the transfercase switch

 

I found the other broken end, although I'm still lost to where it ends up because it goes into the firewall with a bundle of wires. Maybe to vent controls?

 

Cruise Control line?

 

Post a pic please.

 

that my friend is your accessary vacuum line going to the heater controls. It allows you to switch be defrost & heater via the vacuum flapper valve.

 

Thanks buddy. I kinda figured that since it was the only one going into the firewall. I appreciate the answer though.