Sorry, I can't answer your question re:small lung obstruction. It depends on what the x-ray/MRI showed.
I can answer the question re:difficulty breathing out. This is a frequent problem for most asthmatics. There is a breathing exercise called pursed-lip breathing used to prevent shortness of breath when you do things like exercising, climbing stairs, and bending or lifting. By "getting the old" (carbon dioxide)out, your lungs are able to allow more fresh" (oxygenenriched) air in.
Step 1: Relax your neck & shoulder muscles. Inhale slowly through your nose for two counts.
Step 2: Pucker your lips as if you were going to blow out a candle. Exhale slowly & gently through your lips for 4 or more counts.
Remember: Always EXHALE FOR LONGER THAN YOU INHALE. This allows your lungs to empty as much as possible. EXHALE DURING THE DIFFICULT PART of any activity, such as when you bend, lift, or reach. NEVER, NEVER hold your breath.
Hope this helps.
Education info only & not meant as medical advise.