As a former smoker, I can sympathize...
If you've been abusing your lungs for a long time, it may take a while before you see results. Keep doing what you're doing in terms of working out, and change will happen gradually. Congratutions on quitting smoking. I've read that after seven years your chances of getting a respiratory illness are about the same as a non-smoker.
As I said, look forward to a long-term change.
The following advice is based on my experience and training in Chinese medicine:
I would consult an acupuncturist, especially if you got good results when you were trying to quit. Treatment will be primarily constitutional and will treat the underlying pathogenic conditional (heat, dryness, or phlegm) as well. Ex-Smokers are frequently Lung-Yin deficient and do not yet have the lung capacity to support exended aerobic activity, but there are several other patterns that an acupuncturist could conceivably treat.
There are numerous Chinese herbal therapies that can sucessfully treat damaged and weakened lungs. I would consult a Chinese herbalist if your acupuncturist does not practice herbology. There are literally dozens of herbal formulas that may be prescribed to fit the pattern you are exhibiting, and only a face-to-face examination by a qualified herbalist can determine which one is appropriate for you. If your lungs, throat, nose, feel hot, dry, and irritated (or any of the three) often enough for you to notice the difference, you may still have heat in the lung in conjunction with the underlying deficiency. Cordyceps is a well known herb for treating deficient Lung Yin, and is a good all-around tonic for the Lungs and Kidneys. It's also very expensive (about $90 for sufficient herbs to steep in an alcohol solution for about six months to a year). The traditional time to take this herbal wine is in the autumn when the air starts to get colder and drier and starts to effect the lungs, so this would be the time to start making the wine.
The following patent formula is generally used for a dry cough, but could prove beneficial for your condition if the description above fits. One tablespoon is mixed with a cup of hot water and taken anytime. It is a sweet, fragrant tea. The URL is:
http://www.itmonline.org/jintu/ninjiom.htm
You might also consider dietary changes to help build your lungs up gradually. Generally this will take a couple of years, in my opinion (sorry - but I'm trying to give you honest advice), but you will feel much better in the long run. The definitive text for treating disease with Chinese dietary is
Healing With Whole Foods, by Paul Pitchford.
Finally, Qi Gong is of definite use but again, will take some time. I can send you a short video of the Qi Gong that I practice for a nominal fee. This is a "Five Element" Qi Gong that relates primarily to the Five Zang organs (Lung, Spleen, Kidney, Liver, Heart). Feel free to email me privately if you have any questions.
Best,
Steve Lamade