Not to worry...mucous is very common with the cleanse. The entire digestive tract has a mucosal layer that secretes mucous for lubrication. Certain foods, toxins, bacteria, etc. will cause an increase in mucous secreted and also make it thicker. This doesn't just happen in the nose and throat...the entire body can become congested. For the same reasons, the lymph fluid can become thicker and the lymphatic system can become congested. LOL...snot everywhere!
Bingo on the cayenne...one of the reasons it's included in the Master-Cleanse is because it breaks up mucous!