1996 3.1L Plenum (Upper Intake Manifold) vacuum hose

I asked this in another thread, but realized the exposure would be better if it had it's own thread.

On my 1996 Lumina, 3.1L, there is a hose coming from the plenum (upper intake manifold). It is located on the side closer to the firewall, on the passenger side of the engine. It is a vacuum hose, about 1/8" outside diameter (OD). It wraps around the firewall side of the engine, by the coils, comes over the throttle assembly, and dives toward the inner fender. It is at that point that it is disconnected. Can anyone tell me where this goes and what it provides the engine? I understand that it affects the fuel/air mixture somehow, as when I remove the hose completely, the idle suffers badly.

Thanks.

Well I partially answered my own question. The emissions diagram on the front of the engine compartment says that goes to ACSRY. What that is, I do not know. I also found that it goes to (comes from?) a "T" connector. On one of the branches is this hose, on another is a small hose that goes to a wiring harness, and on the other is a hose that is broken off but looks like it went inside the front fender, driver's side.
The hose that goes to the wiring harness looks like it goes through the fire wall (!?), but I was unable to track it with the wrapping on the harness, and the brake cylinder is in the way.
The hose that goes into the fender *may* have come from a black, round, plastic piece secured under there, about the size of a canteloupe. That also has a hose broken from it that seems like it may have come from the "T" at one time.

SO, does anyone have any idea what all of this stuff is? Haynes doesn't say.

I finally found a dealer service department who would take the time to answer and who knew the answer. They said that it is a vacuum reserve, used to move things like the shutters in the passenger compartment air distribution system. This would explain why the heat seemed to keep coming from the floor, even when I requested the panel. This also explains why one of the hoses appears to go through the firewall. It probably does. Good that I found this before summer, when I need the AC!