Reduce all plug gaps to 0.6 and check - you shouldn't face any back fire issue now.
If your problem get resolve by reducing plug gaps - then your coils are weak but you can continue it with minor pick issue.
In case - ur problem still persist then issue can be due to faulty camshafts sensor.
In case of short coils - u will also feel missing and low pick - bad coils are not only responsible for miss fires.
You should not face back or miss fire issue by reducing or increasing air flow if your coils and sensor are perfect and plug gapes are as per standards.
Reducing or increasing air flow can only solve your backfire problem temprory.