The reason why your backfiring is because "your dumping metered air.
Your ecu delivers enough fuel to mix with the air being fed through the intake. If the air is not there, then the fuel does not fully burn, collects in the exhaust and is then ignited. Causing a backfire.
you’ll find our cars only backfire while on decelleration. Mine happens at
around 15oo rpm.
Perfectly normal.
If you having stalling problems, you BOV is set too soft and bleeding a idle.
Hope that helps
-deez