Thanks for the great writeup - used it to open my canister. I am confused about the bb on the Tank side... it didn't look like anything was wrong with mine - the spring was in place, the ball bearing was restricting inbound flow, and my canister was pretty clean inside, but you couldn't blow almost any air from the tank hose into the canister. I am very confused about how that was originally designed to work. The way the ball bearing is situated would normally restrict inbound airflow into the canister - in my case, it wasn't FULLY blocked, but it was VERY difficult to blow any air into it (but not impossible)... so maybe the original design called for a very restricted airflow to the canister? But the FSM says "if the airflow is in any way restricted, fail the test"... very confused.
Also... what are people using for filters? I have some 1mm polyester felt with no adhesive or anything, which seems like a decent idea to use... any thoughts on that? I can't seem to find any automotive grade filter paper where I am, and I don't feel right using a coffee filter as they're too thin - or am I overthinking this?