Sorry for the delay in getting back to you. Please hold your ratings until the end. As for your follow up question, typically the converter will not cause a misfire on #6, but the misfire on #6 will cause the converter to fail. My follow up to you was to let you know that once you find out of if the converter is bad you need to fix the problems that caused the failure like this misfire. It may be due to an ignition system issue or a problem with a leaking intake manifold or a valve issue. Do you plan on fixing this yourself?

Due to the various symptoms that you have and the codes that are coming up I would recommend having the misfire fixed first as well as having the fuel pressure checked. The fact that the vehicle runs different with more fuel indicates a problem with the fuel pump. These are the place to start as they will cause the converter to fail. There is no sense in installing a new converter and having it fail again until fixing these other problems first. I would ask the shop to diagnose the vehicle and use what you now know to determine if they are being truthful. if you have questions about what they tell you then let me know and I will help you.