Greetings all. I have a quandary and I would appreciate any assistance in solving. My car, a Porsche 997.2 Carrera S with the 9A1 DI engine takes cartridge filters. OEM Porsche filters are manufactured by Mann or Mahle and are expensive and difficult to source. Easier and cheaper to source are Wix (57694), Fram (CH11038), Purolator (L25691), and K&N (PS-7032). All are the base filter models by each filter manufacturer (ie no Fram Ultra unfortunately but the market for the filter is likely too narrow to justify the design and construction of an Ultra filter for this application) which is somewhat annoying although the OEM filter has a cellulose filter media, same as the OEM filter which costs three or four times the cost of these other solutions. So, my question to you, learned commentators, is if any of these filters are appreciably better than any other? Cartridge filters seem to vary much less across brands than the canister filters, likely due to their simpler construction. From what I can tell, all seem to filter at approximately 95% at 20 microns although I can't find much data on the K&N. Heck, the K&N, Wix, and Fram all look very similar in construction with pleating, plastic end caps, etc. Purolator appears to have some sort of cardboard or some other fibrous end cap material. Are K&N filters still constructed by Champion? I believe I have included all of the major filter manufacturers but if I am missing one that would be superior please do let me know. Thank you in advance for the recommendations.