The converters fail from overheating. If your car has a misfire, it will damage the converter and that sounds like the reason it failed. The dealer should have been able to determine that.
As far as the parts, that's the chance you take in bringing your own parts.
Let him diagnose it for the failure and see. Tell him to check everything such as compression, fuel pressure, injector leak down as well. Something there is causing this issue.
Roy
Tuesday, April 30th, 2019 AT 5:13 PM