Tom W, thank you, I remembered and spoke incorrectly. I said fuel/air ratio but industry uses air/fuel number. My bad.

The following is a link to an interesting article about measurements taken at various operating stages of a catalytic converter. Shows various inputs and outputs, under start-up, normal operation with and without the air injector pump, and operation with 1-cylinder misfire. I was interested in the HC numbers.

http://www.asashop.org/autoinc/oct97/techtotech.htm

Best Regards,
Jim