Raw fuel is REALLY hard on converters. How much has it been run since the ECM was replaced? If it's red hot, it's either 1) full of unburned fuel it hasn't gotten rid of, 2) plugged, or 3) a combination of the two. I've seen plenty of bad converters that run OK cold and will barely run at all when warmed up, and that would be my guess here is that it's plugged and needs to be replaced.
2011 Hyundai Sonata, Castrol Edge 0w40, Hastings LF565
2017 Toyota Sienna, Castrol Edge 0w20, Hastings LF607
2018 Hyundai Sonata, Mobil 1 5w30, Hastings LF565