If I remember correctly, there is a vacuum
canister, and a vacuum
tank. Both are in your fenderwell. The
tank looks like a black ball and has just one line running to it. It acts as a vacuum reservoir for the A/C and heating system behind the dash. The line has a black check valve that is mounted on your firewall on the passenger side right below the hoodline. One line from that runs to your vacuum tree. You should also see a line running from the check valve down thru the firewall to the inside of the car. And one more line going thru the fenderwell to that tank itself. You'll need that tank connected, or your stuff won't change from floor, to defroster, or etc.
The
cannister looks just like a canister and has a line with a blue and black check valve running to it in between your passenger strut tower and the fire wall out to the fenderwell. If you aren't going to be running your smog (air diverter/bypass stuff), you shouldn't need the cannister connected. Your EGR is the only thing left in that area, and you can run that off the vacuum tree (or manifold), into the EGR solenoid, and then to your EGR valve.
I uploaded a few diagrams that I got from this great site:
http://www.veryuseful.com/mustang/tech/engine/This one has the canister....
This one has the tank........
