vacuum hose goes nowhere 2003 s10 xtreme

2003 2wd s10 xtreme w/ 4.3. found this mystery vacuum hose by the master cylinder that goes nowhere. I was removing some aftermarket wiring and saw this little joiner piece of hose rotten so I replace it, but the other end of the t-fitting went nowhere, but it was also pretty rotten, and the end was swelled up like it had been plugged onto something for a long time. the hose comes from what looks like the intake, comes back and sits on top of the brake booster, then has what looks like a little check valve, then the t-fitting, the little hose I replace connects to a hard plastic like that joins the harness and goes inside, but the other end of the t-fitting hose is loose, and the other part of the hose is fixed in place so I can't move it anywhere, but I cannot for the life of me find where it goes.

S-10s had their vacuum ball mounted under the hood by hood hinge on driver's side. Is yours missing- that is where the hose plugs in.

https://www.bing.com/images/search?q=vacuum+reservoir+s-10+pickup&id=92F2CAAE114E8EC4D0CDB8E55B41DB7C870EB191&FORM=IQFRBA

S-10s had their vacuum ball mounted under the hood by hood hinge on driver's side. Is yours missing- that is where the hose plugs in.

https://www.bing.com/images/search?q=vacuum+reservoir+s-10+pickup&id=92F2CAAE114E8EC4D0CDB8E55B41DB7C870EB191&FORM=IQFRBA

Now that's interesting. That is in fact the hose I am referring to, but I didn't notice that ball. Last night I was looking for a picture and I brought up one on google that outlined the hose in red, but instead of going to that ball it plugged into a little plastic panel on the inside of the drivers fender by the hinge. I don't have the truck sitting here at the moment, but I'm going to be tackling this shortly. Is that ball just a vacuum reservoir or something? I haven't noticed anything not working or any issues. Could I just plug that hose off or would that cause more issues than not being hooked up.

The hose plugs into the vacuum reservoir there should be a check valve inline and tees into the conduit that goes under the dash and drives the mode doors for your HVAC system. Can you change the mode inside (air delivery) from floor to vent to defrost okay? If not, your vacuum is not available. If hose is just sucking air, that is bad, in that you create a vacuum leak into your intake which make you run leaner.

The hose plugs into the vacuum reservoir there should be a check valve inline and tees into the conduit that goes under the dash and drives the mode doors for your HVAC system. Can you change the mode inside (air delivery) from floor to vent to defrost okay? If not, your vacuum is not available. If hose is just sucking air, that is bad, in that you create a vacuum leak into your intake which make you run leaner.

The mode doors do switch fine. I might just plug that line off, I don't have that ball hanging off the hood. As for running lean, this truck has exhaust manifold leaks, and no cats, as well as who ever removed them hung the o2 sensors above the frame rails so they aren't even in the exhaust pipes. Truck has over 200 000kms on it as well as various oil leaks and stuff, not really looking to spend money, it sits most of time.