I measured the two inlets into the air-box and each measured 14.7cm2 x 2 = 29.4cm2 The intake/grab handle, in the right hand plastic, measures 23.6cm2 + all the leaky areas around the rear plastics. Now if the 39mm dia. carb. measures 11.94cm2, why do you need to cut everything open when there is already more than double the airflow available than the size of the carbs venturi? Without an air filter installed, I think it would help opening up the box a little, otherwise I think the difference is negligible. I’m thinking the most restrictive thing is the air-filter. Does any of this make any sense?