What's this tube on my OBX Header (Passenger side)?

[RussMcB]

I bought a lightly used set of OBX headers and they are somewhat installed.

On the passenger side there is a tube and I'm not sure what it's for, and what I need to do with it. It's 3-4" long, about .75" diameter, attached to one of the primary tubes, pointing towards the front of the car.

I can post a pic if necessary.

I have removed the air pump, so if it's related to that, I guess I need to plug it. If so, any suggestions on how folks have plugged it (other than removing the header and welding a plug)?

Thanks.