Is your nose stuffy a lot? I have the same issue with coughing up mucus that you have. My ENT told me it was post nasal drip. He doesn't know much about yeast though, or at least he won't let on that he knows anything about yeast.
I'm sure my trouble is yeast related, especially since it seems to get a bit worse when I break the diet.
You might try controlling your stuffy nose, if you have one, and blowing your nose instead of letting it go down the back of your throat. Somebody on this list (I'm sorry I've forgotten who) suggested using cayenne pepper to help with sinus trouble. That has helped me. My nose isn't nearly so stuffy now.