I found this how-to, and I was wondering if anyone here has done it and if there would be any gain from it besides noise? thanks!
http://www.diymytoyota.com/corolla/the-real-airbox-mod-update-with-cone-filter-in-airbox/
http://www.diymytoyota.com/corolla/the-real-airbox-mod-update-with-cone-filter-in-airbox/