Sorry, I can't believe I forgot to mention that. It's a 1984 380 SL with 125,000 miles. I've owned the car for about 10 years. The 1% CO, which I know is high by state emissions standards, was measured after the cat at the back of the car (stuck the probe into the tailpipe). According to the Mercedes engine manual I have (I have the documentation set for the car), CO can be in the range of 0.5% to 1.5% at an oil temperature of about 80 degrees. That's where I have that number. The car, historically (over the past 10 years), ran at CO levels below .5%, usually .2, .3, or .4%. A new fuel distributor and injectors were installed along with the catalytic converter.

I agree with you, and will confirm and share the results, that the catalytic converter was either defective (one possibility) or was damaged by the fuel/air mixture. If it is the latter case (and we will never know), then this confirms that a fuel/air mixture that is off in the car (very high) can very rapidly destroy a catalytic converter. Rapidly means a few hundred miles, not months or years or 1000's of miles. Again, this is all guesswork so we may be wrong.