SCIFI,
YES! That could indeed be a BIG source of your requirement for a BIGFOOT!!!
There should be a 13mm pipe of sorts in the front boot area (under the covers?) which connects to the under dash booster via rubber hose. From there the pipe runs into and along the inside wall of the center spine, exits with the water tubes and continues down the LH side of the rear lower frame structure, turning upwards at the rear of the engine aprox at the engine/bellhousing joining line.
It continues upwards perhaps a foot or so, which is where it is supposed to connect to a 3/8" -13mm ID rubber vacuum line which travels up and connects to the rear of the intake fitting (that should be there!).
There should be a check valve on the booster itself, and these are known to go bad.....effecting a vacuum leak to the engine......but these can be checked easy enuf...... Ping me back if you need more on that....
Note in pic below, black tube at bottom left frame member, curves upwards, thru red shop towel and is capped with a green cap just peeking out over the frame reinforcement on the shock tower. You can also see where it snakes around to the front and into the spine tunnel. At this point I believe there is a rubber hose joint of sorts there. I had removed the pipe to paint it......so it is NOT one continual piece to the front of the car.
Cheers!
Steve