1997 318ti cold air intake

[Wynand]

Hi

So I recently bought a 1997 318ti Sport. I really enjoy the car, but I want to install a cold air intake which I already have...

Now I've read and watched how to do it, which seems pretty straight forward, the only thing I never see, is what they do with the little plug that plugs into the front of your air filter box.

I know where the Mass flow sensor is on the pipe going into the box, but what is the purpose of that little plug at the front? Do they just remove it? What does it do?

Please help!