John, I really dont know if our varieties are different. I do know that I have to change the cab filter quite often because of bean dust and if I dont vacuum the cab plenum often enough, the bean fuzz looks like snow drifts in front of the filter. As I asked Mike, do guys who have trouble do a thorough job of cleaningIJ When I do it every couple of years I remove the oil cooler and air cleaner assembly so the entire top of the cooling plenum is accessible. Next, I open the side plenums behind the exhaust manifolds. Then the cooling plenum is ready for cleaning. In my opinion, trying to clean without completely opening the air plenum would be a waste of time and could be the reason some guys have problems. I know many guys arent as fussy about cleaning as I am because when I look at engines on dealer sales yards, the dirt is packed between cooling fins. I might have some fins plugged after 2 seasons, but the lions share of them are open. I wish the cab filter would stay as clean as the engine cooling fins.