How do you repair a clogged catalytic converter?

You can't effectively repair a clogged catalytic converter. They're designed as a single unit, and the internal honeycomb structure that gets clogged is extremely delicate and difficult to access. Attempts to clean it usually fail and can damage the converter further. Any attempts to "repair" it are likely to be temporary at best, and could potentially void any existing warranties.

The only practical solution to a clogged catalytic converter is replacement. You can either purchase a new catalytic converter or a reputable used one (be cautious when buying used – ensure it’s from a reliable source and hasn't been tampered with). Installation usually requires a mechanic due to its location under the vehicle and the associated exhaust system work.

While some additives claim to clean catalytic converters, there is little to no scientific evidence supporting their effectiveness and they may even cause further damage. It's always better to address a clogged converter directly through replacement rather than relying on potentially ineffective and possibly harmful solutions.