I concur, and had almost this exact same problem. I'd be congested all the time and it caused me a lot of problems. Out of curiosity, have you ever tried edibles instead of smoking? That solved my mucus issue almost instantly.
My personal issue w/ edibles is that I was unable to control dosage, timing, level of my high as well as w/ smoking in my experience. To get to a level of satisfactory stoned, I would have to ingest 75-100mg of THC at one time, but then that is lasting several hours, coming in waves, etc.