[Somchai]

The removing of the secondary butterflies I would recommend for racing purpose only and with saying this, only in combination with a modification of the ECU.
The only one and really professional company in tuning the Ninja 250 and 300 (Scuderia Platini in Italy) are doing this for their race bikes, but at least they don't talk about the power gain from this part of their modification.
If the pod filter would give a power gain, then this company would also use it - but they don't and from German WSBK bikes I remember they also didn't since they'd measure a small loss of power.

For the average rider it's better to keep the secondary butterflies in since street riding is much different to racing.

And a last word about the planet-thing, to expand the own horizon one should also be so free and take a look outside the own borders.