I just have the big hose going into the airbox, that one is obvious. But I noticed that underneath that there is another hole, like something is supposed to connect there.
Secondary air injection pump
2004 Passat 1.8t 4motion
2002.5 GTI 24v VR6 6 speed
The part circled is what I'm talking about.
Are you sure something is supposed to connect to that?
Mine didn't have a stock air box when I got it, so I'm not totally sure. That doesn't look like it would connect to a hose. Looks more like it's just an air inlet.
Nothing goes to it. If the airbox starts loosing air flow from the normal inlet, that flap opens up allowing air to flow in. It has a spring on the inside.