'92 PAU Charcoal Canister

I'm trouble shooting an idling problem with my '92 Park Avenue Ultra. Right now, I'm stuck on figuring out what is normal operation with the charcoal canister.
On my canister there is a hose fitting for a tube that runs to the gas tank. There is a fitting for a tube that goes to the supercharger's manifold, engine vacuum.
There is also a fitting called, "air," that's covered with a little cap, but basically open to the atmosphere.
I removed the canister for testing. if I blow into the fitting that normally goes to the gas tank, air comes out of the "air" fitting. If I blow into the fitting that goes to engine vacuum, it's restricted, probably due to the solenoid not being energized.

So, is this to be considered normal?

Next, when the car is in operation, and the canister is connected to the hoses and electrical connectors, there's a pulsing of the solenoid going on, seemingly constant. Is this normal?

From reading the shop manual, I get the idea the solenoid is supposed to operated just every once and a while, not necessarily all the time especially idling.

I've got the rough idle blues and maybe I'm grasping at straws but something just doesn't seem right. I think I've checked all the other suspects (within reason). But, this car, when it comes to a full stop, really wants to die. The engine RPM's drop and the idle is very rough. Then it kicks up and sometimes balances out for a while.

I've read where this should be a vacuum leak and I've replaced all the rubber couplers and tried the unlit propane torch and get nothing. I can't seem to isolate what's going on.
Thanks for your help!!

On my way into town on Saturday I stopped by the junkyard and took a look at some other cannisters. And sure enough, they all have the vent and all have the same characteristics as mine. So I'm chasing down the wrong rabbit hole. Sigh.......