I stole some pictures off of other posts here trying to find my answer as it is nasty outside at the moment. I just got the head gasket and valve cover gaskets done on my 93 pickup. There is now a little bit of a surging idle which seems to be coming from a vacuum leak. If anyone could help me with where these vacuum lines go I would appreciate it. I have looked at the diagrams but still cant figure out the last one. it is labeled as top in the first picture. it looks like in some of the diagrams it is capped off, but if it actually goes somewhere I would like to try and fix the surging idle by hooking it up correctly. What exactly is the black piece the vaccum hoses connect to as well.

 

I'm having the same issues with my 89 3.0 3VZE...CEL codes 51/52/71.... #3 looks to be your brake booster

 

Your pictures are broken, but a surging idle could be the Throttle Position Sensor out of adjustment, thats what mine did until I readjusted the tps. Now she idles smooth as butter.

For real tho there are tons of vac diagrams and pics of peoples vac setups. Just go to google images and search 3VZE vac diagram, you'll find all the info you need.

 

are you asking about the black plastic piece with the three nipples? it's just a splitter

I believe the one labeled "top" goes the a switching valve. i'd have to verify when I get home and can look at mine.