Head Pipe & Catalytic Converter Kit

Cataltic converters use precious metals like platinum, palladium, and rhodium (look towards the heavier end of the periodic table for these) to convert toxic molecules like NO_x and carbon monoxide into inert N₂ and CO₂. The exhaust gases flowing over the metal coated ceramic grid don't actually use up any of the precious metals during this process, hence its name: catalytic converter, since the metals are catalysts that start the reaction without being consumed.

That said, burning coolant or burning oil can plug up, coat, or otherwise damage the delicate coated ceramic monolith inside the catalytic converter. If you're running way too rich or too lean, you may even in extreme cases melt or blast out chunks of monolith

If you see "catalyst below efficiency" OBD2 error codes that won't go away after replacing the downstream O2 sensors and eliminating any vacuum/boost leaks, or if you can hear loose chunks of monolith rattling around inside your downpipe, it's time to bite the bullet and replace your cats to get your car road legal again.