2003 Expy EB no stability control or traction control options

There is a tube that comes off the anti-lock brake controller then splits and one part of it comes up and is clipped to one of the brake lines at the Master Cylinder ( see Pics )

Doesn't connect to anything ?



Is it something that would have been used if there were stability control or traction control options?

 

Is it a wire or a vacuum hose?

 

Its hollow so must be a vacuum hose, I'm guessing for traction control or stability control? Neither of which my EXPY has.

And if its a vacuum hose and runs to the anti-lock brake controller should I plug it?

 

Plug it in to where?

 

Did this truck have air suspension at one time?