Vacuum Line placement?

I have been tyring to fix the cruise in my 85 911.I found an open vacuum line on the Tempo stat motor or servo motor as it is referred to as.The unit has 1 electrical conn and 2 vacuum lines 1 small 1 large.The large one is connected at the servo but the other end is open.I have looked but can't find where it goes.Can someone guide me to where this line goes.How does this tempo stat device work?
Please lend your advise!
Thanks!