I only get this feeling on the left side though...of having trouble breathing, the tightness and fullness. Some of you know I had LTN injury on the left side and I totally think its related. When doctor Nath removed the muscle and freed the LTN it was like I could breath again..But stress causes me to tense up and the muscles in my neck will still squeeze the LTN...He told me to be mindful of what I do because the LTN is such a delicate nerve and easy to injure. So Tam this could very well be your problem or its the smog..only one way to find out and that is tests unfortunatley. Or just be mindful of the cause and try to practice relaxation techniques to help the muscles relax.