I wanted to add that he may have bronchitis, or some other type of breathing infliction - so an xray of his lungs would probably be a good step..
I know how heart breaking it is to see the poor thing coughing when he's supposed to be at his happiest (when he's purring). It got to the point where I didn't want to do anything to make him purr because it was so sad when he started having a fit..
Taken over by:
Jake - grey DSH (Aug '98)
Alley - spazzy grey tabby (Aug '07)