Where did the hose go?

I have a 4 cyl with a weber carb by prior owner. Been running perfect then started running like crap. You can see an empty nipple behind the carb that when I put my finger on it the engine smoothes out. I am assuming the line came off but where does it go. And, how did it disappear?

Still looking for help here. This is on an '86 AMC 2.5L. Ran great then one day it stopped running smooth. Cover this valve and it runs nice.


In this pic, what is this "valve" on the intake manifold. Trying to figure out where it needs to route to.

Thanks

If there isn't a loose line anywhere, then there may have been a rubber cap that cracked and fell off. Cap it off for now. It probably went to the stock air cleaner or carb or something that has been removed.

Thanks. That's a good thought. Because my EGR is missing its line I was looking for a missing hose. Never considered the plug came off. I was too focused on adding lines back.

As a follow up, when using the Weber carb does the need for the EGR get eliminated? Or they just short cut it by cutting the hoses off the canister.