Check this out before looking into couple of the brand name filters.....
The blitz one did bad but it was wierd to see that the hks did the worst!
http://mkiv.com/techarticles/filters_test/2/

yeah hks mega crap flow. it's a show item , and to me it isnt even a good looking filter.

neat find.

Thanks for the link.

Blitz claims filtration down to 100 microns, which is nothing to brag about because that's about the size of a grain of salt (!!!). I didn't expect much there but I was surprised that the HKS foam filter did so poorly.