Vacuum connection?
 

On my 87 GT behind the dist on the upper manifold there is a vacuum line attached, this line on my car is plugged. Where does this line go and should I reattach it.

You probably dont have cats or emission equipment on the car. That line goes down to the charcoal canister down by the front of the car. Most people take that out when they go to off road exhaust. Don't worry about it. Just make sure the line is completely blocked off and it is not leaking.