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I believe this is the TSB for the root cause: https://static.nhtsa.gov/odi/tsbs/2025/MC-11015519-0001.pdf There are reports of melted cats as a result in the FB groups, likely on this forum as well, too lazy to go search for them.

The JB4 isn't melting any cats and all maps were developed with EGT monitoring. The Hurricanes have a weird factory defect where the ECU programming randomly dumps unburnt fuel at idle and melts the cat. I believe it's been fixed, but there were lots of reports of the issue on factory-tuned trucks.

Just to clear up any misinformation here. 1) The issue with the defunct factory ECU programming causing issues with the factory cats has nothing at all to do with the JB4. The JB4 is not active at idle/low load when this issue occurs and the JB4 will neither help nor make worse the issue. The...