I thought that the reason they got narrower was to create a venturi effect which accelerates the incoming air into the plenum / inlet, which has more effect than boring out the throttle body.
What about fitting an induction kit?Would that be of any 'benefit' ?
if you stop in the water for some reason or you nose into somethin a bit sharp a splash is all it takes to scrap the lump. i aint sayin ya gotta have one but i just think it is one less thing to worry about. I have no intention of going that deep in water but before I fitted one I had managed to get water and mud into the airbox. Only good fortune and a paper filter stopped it trashing my engine