The smell is definitely being caused by the catalytic converter but that doesn't mean it's bad. It could be reacting to fuel with higher than normal sulfur content. I used to hear this complaint quite often in the early nineties. You say the car runs good, with no loss of fuel economy or power. That eliminates a clogged cat. If the car will pass an exhaust emissions test I'd forget about the cat, unless of course the odor is unbearable. You might try changing the brand of fuel you're using to see if there's any change.