I just saw this. I agree analyzing the problem is the way to go. My initial recommendation was based on a bad assumption that you had a high mileage FJ. Those old sensors didn't look too good anyway. My error codes started showing up after the first time I ever ran out of gas. I'm sure there was all kinds of junk at the bottom of the gas tank that was sucked into my engine and out the exhaust. It sounds like your problem is specific to that side of the vehicle. I guess you could have an exhaust leak or a vacuum leak. Hopefully it's not the CAT. The OBD2 reader should help you determine what's wrong. There was a link in of the the other forum threads of a YouTube guy that explained trouble shooting real well. I remember he wouldn't look straight into the camera. Sorry no link but you'll know whom I'm talking about when you see him. Over several videos he explained everything on how vacuum leaks, air leaks, weak pumps, bad mass flow sensors, bad O2 sensors, and bad air/fuel sensors looked on the OBD2 plots.