Deceleration valve leaking?

The CAT reduces hydrocarbons and 3 ways (1981) reduce NOx and actually need to run a little rich to work (!) So a little rich wont hurt it unless it goes into meltdown as in a rich mix at all times. Were dealing with just very short periods of rich mix, as in less than a second an event. I remember my sis's carbed Toyota Corolla always 'coughing' on lifting the gas when she shifted as well as most of the manual trans Toyotas of the time. Maybe all their decel valves were wasted or they didnt use them. I know Datsun used them and i got a few hits on their workings on Datsun sites.