I never said they were dumping fuel directly into the CAT. That wouldn't even be possible. I only pointed out that burning excess fuel (or just running too rich) is known to harm CATs and that maybe that is what the strat crackle tune is doing for the Rice Crispy treats that get so much love around here.
According to them, they get the crackles by DECREASING the amount of fuel on throttle lift. The focus RS in sport mode has just as much pop and bang as the strat tune does. My other car, which runs on megasquirt, I was able to get the same effect by decreasing the amount the injectors fire when TPS value is at 0%.
For what it's worth, I've got 4k miles on my tune with crackles. No issues so far.
edit:// Keep in my mind that this code is not always the converter. The ECM doesn't really know if your cat is good or bad, it just relies on the 02 sensor to tell it if it is. Exhaust leaks can cause this, as well as an 02 sensor that's on the way out. Granted, it is suspect because you just flashed the tune.