My honda mechanic said there would be a loss from hot air.
He suggested cutting the plastic inside the box seperating
the the first part where the air enters and has to swirl
around to meet the filter. That way it directly hits the cone filter at a faster rate. He told me the plastic is there to quiet the airbox but would be a gain of performance. It would not sound quite as sweet as the top off but no hot air in the box which is the goal plus better
air flow. I have not had the guts to cut it out yet since
it is non reversible. Anyone else with any thoughts about that????