what is the grey thin looking straw pipe that starts from under the hood (near the MAF sensor), behind the top manifold, under the car battery leading into the firewall? the reason why I am asking is because in my car there inst anything connecting to it. should there be something connected to it.

 

It is the vacuum source for powering the air diverter flap inside the heating/AC unit in the car.

 

does the end of that straw get connected to a thin black vacuum hose located near the MAF?