1989 240DL vacuum hose mystery

[durden022]

Newbie to the forum

I recently bought another 244 sedan (regrettably sold the first one). I am trying to figure out where or what is suppose to be connected to the top vacuum line on my intake (large hose with plastic "filter" looking thing and then another large hose that sucks in air). Most pictures online suggest it goes to the cruise control, but I don't believe this car is equipped with that. Does this need to be plugged? Car seems to have lower idle with it closed off, but also maybe a little rougher idle too.

Any help would be great.
Thanks,
Matt