Venting Gas Tank

What ever pressure (in tank / out of tank) is the greater will fill the tank non-fluid occupied volume. The one way check valve may not "seal" after many years. Again no-one to my knowledge calibrates/tables to the solenoid. The system does nothing without tables.
Are you drunk?
Engine vacuum produces the vacuum which draws the fuel vapors into the throttle body when the calibration opens the valve.
You will pull vacuum in the tank, fuel pump will not be able to overcome it, and you'll starve the engine. Best case, it cuts out while idling. Worst case, you lose fuel pressure under boost and need engine work.

You can diagnose it by checking if the line to the charcoal canister is open (blow into it?). You can also let it run for a while, then open the gas cap and listen for a woosh when it sucks in air.
Thanks Jonasterg you said it better than I ever could have. I was just about to press post and boom you explained it much better than I me.
But if you blow back in the direction of the tank you can push crap into the tank. if you use compressed air. I dropped the tank and tried blowing both directions with no success.
I had to drop the tank and run a new line from the tank vent to the charcoal canister. I believe it is the middle line off the sending unit.
I did this last week. I disconnected the vent line at the tank and at the charcoal canister. Put a piece of paper towel over the line at the canister and blew compressed air through at the tank end. Flowed freely and whoosh...paper towel blew off.