Backfire - Outlander 800 MAX XT with HMF

[kokonai]

I mount K&N air filter, HMF Optimizer gen3 and HMF Utility pipe with quiet core.
The ATV is Outlander 800 EFI MAX XT '07.
When full press on the accelerator and release it there is a backfire in the pipes.
In idle run no problems. In acceleration too. Only from up to down closing acceleration.
The cap of HMF is dirty and smoked.
I use recomended settings - 2/4/3,5, But it seems that the fuel mix are pure. What to do?
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[Mike/HMF]

You will need to set the first mode to the highest smooth idle(RPM) with the engine idling at operating temperature. Minor popping on deceleration is normal. Excessive popping on decel can be typical of a lean low speed circuit.

[kokonai]

The good results are with settings 6/4/3,5
Deceleration pops are minor.

Thanks
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