Today I was doing a oil change and I noticed that there was a vac line not connected to this intake manifold. It was a rubber boot that must have came loose. There are three ports just under the throttle body. The one I am refering to is the one towards the front end. Where does that one go to?

Trying to figure out if this is part of my MPG probably I've
been having here --> https://www.cherokeeforum.com/f67/up...n-ever-120990/

Here is pics I found on the forums here of said port

 

Mine was gone too, but if you look on the hood there is a sticker that says it isn't used, so just find something to plug it with

 

Mine has a hose and a boot on the end of it that went there. Just looks like it came loose. When I put my finger over the port it almost stalled the engine. I put the hose back on and it seemed like it idles a few hundred rpm lower now..

 

the vaccume line is in there somewhere. find it.