for those looking for hi-performance,hi-filtering capability,apex'i,sard sport ex and k&n is the filter of
choice.for those looking for higher air flow but adequate filtering,sponge type filter such as HKS is
the way to go.but like huakenny said,the maintainance is quite high for such filter.last but not least,
the mother of all hi flow filter is the blitz s.s mesh filter.flow the highest but filtering is the worst of all that i mention earlier.