Quick question: There are two vaccuum line connections at the back passenger side of the plenum. The smaller is for the line to the fuel pressure regulator, whats the larger (further rearward) one for?

IIRC, it goes to something related to the smog system. Either the a.i.r. divertor box or the charcoal canister.

Is it the same plenum that has always been on your car? I ask this because I have a speed density setup and I also have 2 fittings and the other one you mention is used for the MAP sensor on mine.

Yep same plenum since '87, but its a MAF car, so I'd guess thats the difference.

Mine feeds the heater controls and the cruise control as well as the vacuum resevoir on the driver's side fender.

with the supercharger, it also feeds the boost gauge, the fuel management system and the diverter valve.

Here you go, this should clear up the confusion.