i take it your ls/vtec is going to be non-turbo, there for i would make sure that you have Some type of back pressure. Your not going to want a lot of it because your purposly trying to flow a lot of air through the head, but remember that hondas like a little bit of back pressure unless your going with the turbo setup then you won't want anymore back pressure than the turbo is applying. hope that helps you make your decision.