I know this is a small image, but it's the only reference I could find. We put my 88 TII on a smoke machine and have located a vacuum leak on the back of the engine. There is a small, short vacuum hose that is disconnected right below these the 3 nipples seen in the image. On my car the top nipple is occupied as seen, but I don't know what belongs on these other 2 and which one I should connect the mystery vacuum hose to. Any guidance is appreciated.

 

you have to plug those nipples off if they are not being used.They are vacuum sources.Otherwise you are just going to run like crap.(vac leak)
why not just hook the hose up to the bigger nipple in the pic?It looks like that is where it goes anyway.

 

That picture is not my motor, but my situation looks almost exactly like that. I didn't hook it up just because it's unknown what it goes to and what those 2 nipples do. The car has already been pillaged by the previous owner...there's half deleted emissions stuff everywhere.

 

Like I said those THREE (if you look there is 3) nipple are part of the upper manifold.They are Vacuum sources.
Now,cap them off if you are not using them.
..and IF you have a hose that is off,then By rights it was NOT receiving Vacuum,Right???
Then it would not Hurt things to hook it up to a vac source to try and see if it does need Vacuum.
Post a Pic of your actual engine,or we would only be Fixing the "Car in the Pic"...and that wouldn't help you at all!

 

Follow the vac. Diagram in a service manual they are very useful