2005 Toyota Camry

Well, what I would do first, is this:

Find a shop that does motorvac fuel cleaning.

There are other ways of cleaning. Let me explain. Carbon can coat a converters inside prescious metals that will prevent them form working. My guess is there has been a fuel/air ratio problem due to the recent repair. By sending a cleaner into the system, various components such as the oxygen sensor in front, the converter, and intake valves.

Another option is too add a can of seafoam to the fuel tank or castle's fireball plus.

Intake cleaner or top engine cleaner can be sprayed into the throttle body and it will get sucked into the engine. Castle's hydroblast is another good product that gets sprayed into the vacuum lines going into the intake manifold.