Hairball or Respiratory Problem?

My furry cat Presto has had a hacking cough the past few weeks. It's the kind of cough he usually has for a few days, right before he yacks up a big hairball.

No matter how much Laxatone or how many hairball treats he has, we haven't seen one of these usual hairballs.

His hairballs are hard to miss.

Let's just say that Presto usually projectile-ejects 5- or 6-inch-long missiles, the diameter of a man's finger. He's been known to swoon immediately following the ejection.

We began to worry, and we've had him in to the vet twice (our regular vet was out of the office the first visit). Neither vet detected any back-up of hairballs when listening to his lungs or poking around his belly. In fact, the temporary vet said his lungs sounded fine. Dr. Burnett (the regular vet) gave him an injection, I believe cortisone. I don't think he coughed once in the next couple of weeks. When the shot wore off, he started coughing again.

Presto is overweight, but he is still active and will run and play (sometimes). He has a plastic allergy that manifests as a swollen chin when he decides to chew on something plastic. And he loves to chew on plastic.

We're not sure what could be causing him to cough more than usual, unless it's the same proliferation of allergens that are giving us all stuffy noses this year.

And I'm still concerned that I haven't seen (or stepped in) one of his usual projectile hairballs.

Has your cat ever had a hacking cough that sounded like a hairball cough, but wasn't?