vacuum leak/ vacuum hose help, urgent

[dukcaln]

so I started the truck up today after driving it last night with no issues.... I got about 30 seconds in the warm up of the motor and heard kinda a pop followed by what sounds like a bad vacuum leak.... so i stopped the motor and took the cleaner off and noticed the below (see picture). what connects to that and shouldn't there be something..... maybe plugged off. I couldn't find anything else



also where does this hose plug into, its been plugged since I got the truck.. mabe I need to get it plugged up in the right spot...