@funk24 I see you mentioned a breathing test. TOS can affect breathing too. When half of my chest wall is too tight because of TOS, it doesn't expand enough, and because the lungs don't move and expand as much, it can build phlegm. I also have allergies and asthma and I did have a repeating issue getting chest infections on the tight side because of this. I did also have another problem that exacerbated the phlegm that surprised me. I had problems with old dental root canals that were failing, and I am having those teeth replaced with dental implants and a restoration. As soon as the teeth were extracted, my lung function improved immediately and my allergies were much easier to control and didn't have the excess phlegm. Sometimes a few issues can combine and make a bigger health issue. I hope you get some resolution and find a path and a plan for recovery. Please come back and share what you learn.