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Adding near 10-12 1/2" holes on the backplate you'll add some more air.
It's an alternative to an aftermarket filter, and the power gain you have is between stock and an aftermarket filter like SE.
On many bike it's a common mod like the Suzuki Bandit, Kawasaki ZRX1200.
For example with Ivan's jet kit for Kawa ZRX1200 you add 12 3/8" holes on the filter cover like in this photo of the kit and instructions:
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