Notice the sellor on ebay,,,,,,,,gmanonline ( Feedback Score Of 57I think they sell those on the G-man industries website. If I remember correctly they are suppose to fit in the stock air cleaner.
I don't remember the exact CFM increase with his, but it was substantial. He flow test all his stuff, He has the flow charts on all of it.They replace the back of the stock air cleaner and use the stock chrome cover over it, thus the "stealth" name. Notice the tabs on the outer ends of the unit where the stock covers would attach, so the air flows in from the back of the cover.
I would say they would flow more air than the regular replacement K&N filters would as the filters look to be quite a bit larger.