Great. Knowing it's a problem is half the battle

I had it open a few days ago when I checked the jets, and didn't see any obvious tears or rips on the AP plunger.

I suppose I should be able to take the airhorn off, take the plunger out of the airhorn, and manually move it in its bore to see where the pressure is going?

It's suppose to warm up here in a few days, so it will probably wait until then.