I was enlightened some years ago reading about forced air induction on superbikes, you know the sort with holes in the front of their fairings, and pipes off to the airbox.
what enlightend me was that in doing so, a small pipe was required to be run to the float chamber, to keep the air pressure difference consistent. i.e. imagine the air pressure being so great in the venturi that without the corresponding pressure being applied within the float chamber the venturi pressure has a negative effect on the fuel coming up through the jets
