[Formulajones]

The only problem with flipping the lid is it now takes the crown of the lid and tapers it in toward the carb, this is usually a HP killer for a couple reasons. One is putting the lid closer to the air horn, the other is the direction of air.

Most likely the reason for a gain, and this gets back to why the pure stock guys are putting taller filters in, is because you've now exposed more filter area around the circumference of the base. The same thing is accomplished with a taller filter that simply lifts the lid up, and still keeps the lid in it's proper upright position. This still helps direct airflow properly, and also keeps the lid further away from the air horn. This method actually works better than the lid flip deal.