Catalytic converters are essentially self-cleaning. As long as the engine is correctly tuned and the ignition system is working properly, then a catalytic converter should last the life of the vehicle. When there is damage to a plug or plug wire, a fuel injector or carburetor is malfunctioning, or the timing is off such that incompletely combusted fuel is passing through the combustion chamber, then the catalysts can become coated initially and destroyed eventually. A short-term issue should not permanently disable a catalytic converter, though. As long as the catalysts are not poisoned and the honeycombs are still structurally sound, the matter should correct itself. As for removing and cleaning a catalytic converter, Berryman Professional Chem-Dip Carburetor & Parts Cleaner (part 0905) would be effective at removing the carbon (but not catalyst poisons such as lead or phosphorus). However, the cleaner has some nonvolatile components that should be removed after soaking. The best bet for this follow-up application would be Berryman B-12 Chemtool Carburetor, Choke & Throttle Body Cleaner aerosol (part #s 0117 and 0120). Alternatively, you might even be able just to use the aerosol as it is also quite effective at removing hard carbon.