I have a similar problem. My head is also "clear" now for the most part, but when I exercise it will bring back the symptoms. Are you certain this is a result of the vibrations/impact while running or cycling? Could it be just the fact that you are exercising and increasing you heart rate and sending more blood to the brain? Have you tried a stationary bike or other non-impact aerobic exercise and does that result in the same symptoms? I have been trying to figure out why this happens to me for the last year. The doctors I have seen are clueless, but it seems as though it might be a result of something vascular relating to cerebral blood flow which changes with aerobic activity. I am still trying a few things like neurofeedback, although I have only done 5 sessions so far - seems promising for things like controlling anxiety, but I dont know if it will solve my exercise problems. If neurofeedback does not solve this problem, I may eventually look into HEG feedback which measures the blood flow in the brain and allows you to regulate it based on real-time feedback.