P0420 code showing after misfire repair

Hello, Dave here, contributing to RepairPal and providing expert advice since 2010. I can understand and respect that you've replaced all these components. Including the catalytic converter in the past. But we don't know if the misfire that you were experiencing was bad enough to run so much fuel through your catalytic converter that it caused another failure. The easiest way to know what is happening here is to measure the exhaust gas before and after the catalytic converter. If there is no change in the reading, the converter is not doing his job. You list possible resolutions - but at the end of the day it all comes down to catalyst operation. If you had leaking fuel injectors, this catalyst inefficiency code would come because of damage. There is no canister concern causing us code. Yes, you could have faulty oxygen sensors before or after the catalytic converter, or a wiring or wiring connector issue. Especially if it's not original equipment. However, you have indicated that you have used original equipment parts. I would clear the code, check for any exhaust leaks at the manifold - or anywhere else, and recheck operation. If the code P0420 comes back, it's likely the catalyst again. https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.