Right above the block-off plate (in between the dashpots) there is a black vacuum cap. what is intended to attach here?

 

The picture is unclear. Is this the same one? It's for the pressure sensor.

 

Move the giant red harness!!!

It does look like the port for the pressure sensor though, can't be 100%....

 

It is the same one featured in the second photo posted. I just got done putting a rebuild in and removing the emissions . I can't find anything to plug in to it..but noticed that it wasn't addressed in the emissio0ns removal procedure.

 

Boost gauge.

 

On a non turobo 1986 RX, it's for the vacuum operated Cruise Control. The other one fwd of it is not used.

I glued a quarter over the subzero's vacuum source years ago. I bet that cost less than your blockoff plate.

EDIT: I might revise that answer later. I've been using it for the cruise control vacuum source for some time. But looking at the 1986 non turbo Fuel and Emissions section of the online FSM, they, in their vacuum diagram, seemingly show two hose coming from that area going over to the other side of the engine. But then again, they also show the vacuum line for the primary injector bleed on the wrong side of the manifold which is wrong.

 

that nipple is the vacuum source for the MAP sensor that is mounted to the right front shock tower.


here is the MAP/Boost sensor

 

Sorry, I thought he was talking about the two nipples capped off on either side of the SubZero mounting boss. Yes, in the second jpg on this thread where there is a red arrow pointing to the hose.....boost sensor line.

Drawings of the vacuum lines for a series four non turbo are found on this site in the FAQ thread. See dwg (some errors on that dwg though).