Your symptoms may well be on the basis of Exercise Induced Asthma (EIA), that for some individuals, is the only expression of asthma. Thus you could have EIA, with relatively normal PFT’s at rest. These PFT values are within normal limits for the most part. The RV is elevated at 138% and that could be caused by asthma. The air flow rates are normal and the diffusion study results are above predicted normal values and, higher than predicted diffusion test values are commonly seen with asthma.
You should probably have an Echocardiogram to rule out heart disease as a cause of your shortness of breath, unless your LV ejection fraction and pulmonary arterial pressure were normal at the time of the Cardiac Cath in July and, at that time, you were already experiencing shortness of breath with exertion. If your shortness of breath began after the cardiac cath, then that is a different story, and the cath data would not exclude heart disease as a cause of your current shortness of breath.
You should have an EIA study performed, preferably on a treadmill, rather than a bicycle. If, by chance you have a peak flow meter (PFM), or your doctor can provide one, you could do a crude self-test comparing your resting PF with your post exercise PF at a time when you are still short of breath.
Good luck