I have a 2016 Suburban that I just had a rebuilt engine put in and the engine is for a 2018 Suburban that they said would be just fine the mechanic would just have to change a couple of things. The problems that I am experiencing is I have a check engine light coming on that says Bank One catalytic converter is bad but I just replaced the catalytic converters in this car less than 40,000 miles ago and then the next issue it has is intermittently the check engine light will start flashing and it says random multiple engine misfires. I have now had the spark plugs and the wires replaced it is still doing it and there was once where Bank two of the catalytic converter came on saying it was bad but that has not come on again. Any advice or what my next step should be to get this resolved the mechanic says I need new catalytic converters on bank one but I don't agree since they were just done. And having a new engine that has multiple misfires just does not make any sense could it be a wiring issue? any advice would be appreciated