Can you tell me what part this is?

[Atomik]

This is the only online pic I could find so please ignore the yellow scribbles. I am wondering about the plastic black cylinder tube with two or three vacuum lines attached that sits right on the side of the evaporator housing. I have an 89 Ranger 2.3L Thanks.

 

[adsm08]

It's vacuum in a can.

 

[4x4junkie]

It appears to be a vacuum reservoir for the fresh-air/recirculate vent door solenoid.
On my '90 the door quit functioning (wouldn't move to recirculation mode) when the vac line from that cylinder to the manifold broke off which I had to fix.