Changed my ECU a few weeks and the car has started poping and banging,It only happens when i come off the gas and slow down with a bit of brake. when I put the old one back on no problem.But the new ecu gives me better mpg and more power. sound okay, but do not what to do any damage. Have a couple a engine upgrades. ECU,Greedy dump valve,De-cat exhaust.HKS Induction. Any Ideas ??? Or is this normal?

I asked the same question about a week ago.

Its called overrun, and happens when you change to a straight through exhaust, your half way to flame i believe ;)

Its excess fuel igniting in the exhaust, i was told that it was nothing to worry about

J