I've done some more reading on the Intek air filter problem, and every reference to it I have found, has related to the twin cylinder version. Here is one description of the problem (read mroman59's explanation of what it is and how to fix it):
http://www.mytractorforum.com/showthread.php?t=263375

He says the spring-clip that retains the top cover of the filter box has insufficient tension to press the element against both the top and bottom of the filter box, so there is air leakage past the filter's ends.