Originally Posted by Poolside
Seriously though, the backfiring issue is caused by the ECU performing a function called Overrun Fuel Cutoff. Each cycle of the fuel cutoff function causes an amount of unburned combustion mixture to exit the exhaust valve and collect in the exhaust. The backfire, or more aptly afterfire, you hear is the combustion of that collected combustible mixture.
Among its magical powers, the IICE Cool effectively disables Overrun Fuel Cutoff.
Hooray for Engineering! (okay, a nod to Marketing, too).