I commented a little over a month ago saying I was having similar issues. All my lung testing looked pretty normal, but I went to a pulmonologist who said that based on my symptoms and the testing she had seen, it was probably either asthma (minor I guess, considering it wasn't really impeding with activity), or reactive airway disease. She put me on budesonide - a steroid inhaler - and that has made a big difference. I've got another week or so on that and then she will revisit, and there's some test that can definitively diagnose asthma - not sure if she'll recommend doing that, or what will be next. Again, Pulmonary Function Test was basically normal, chest x-ray normal, I can run around and exercise with no problem - it was just the chest tightness that was really bothering me.