I just got my 1991 Toyota pickup I'm trying to put this truck back together. Under the intake it looks like there's some kind of water jacket port because water is pouring out. There is no where I can see it plugs into. Previous owner replaced the engine so they may not have put it back together right, they forgot parts or mixed parts from different engines. My manual doesn't describe what it does or where it goes.

 

A coolant line definitely connects to that. If I remember correctly , on my 85 which might Be different since yours looks newer, it goes to the AAV. Coolant like runs from that to the throttle body.

 

Looks like this topic is popular. From under the intake where does it connect?

 

I found where it goes. It was wrong parts installed by previous owner.

 

With the throttle body being straight, that should be the IACV.