recently purchased this 1985 Bronco II (2.8 v6) and after a basic tune up (plugs, oil, etc) and running top engine cleaner it’s running “okay”. It was missing the air cleaner system when I purchased it (working on a solution for this now).

Still stalls if I don’t keep up the throttle at lights, but I notice it runs a little better when I plug this hole on the left side of the engine. It’s sucking in air, but I don’t know what it’s aupposed to be connected to or what it does. Can anyone help?

Directly to the left and below the carb.what is this thing??