It connects to the bottom of your intake manifold and runs up to your brake booster. (The brake booster is a large black round device with the brake fluid tank on top of it.)
For some reason Ford used this corrugated hard plastic tubing crap for some of the vacuum lines. It becomes brittle and cracks.
BTW, the brake booster line has a check valve in it and is a pain to get off of the intake manifold.
HTH,
BP
