No. It's perfectly normal. Just the AIS system trying to clean up the emissions by allowing air into the exhaust ports to ignite any unburned fuel, which is the explosion/pop you hear on the overrun.

Dead easy to stop this. All you need to do is block the AIS pipe between where it takes air from the airbox and the AIS valve. Use a bolt, or whatever you have at hand. Make sure you block the correct pipe though!



Full thread can be read here.

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