So I was mucking around under the hood and found a vacuum line running to under the battery. Confused I pulled the whole battery box out and found it ran to a box, and that's it. what the heck it for? the line runs from the manifold to this sealed box. seems pointless.
Can anyone idenify its purpose?

 

That is a vacuum resevior for the A/C and cruise control. It helps with keeping the air vents functioning while at full throttle or climbing hills. May seem pointless, but it is not.