Read these first;

Not very old having used correct cleaning oil:

http://img.photobucket.com/albums/v2...closeup_lg.jpg

Result of those holes:

http://forums.roadfly.com/forums/por...4959457-1.html

Jap test:

http://www.mkiv.com/techarticles/filters_test/1/

E30 test:

http://www.bolhuijo.com/airflowtest/

Well respected Autospeed:

http://autospeed.drive.com.au/cms/A_2232/article.html

RR results:

http://planetsoarer.com/dynoday/dyno3.html