I pulled my air filter and found that when the tray comes out any debris sitting on the foam can fall into the clean side undetected while changing the filter. I had leaves, seeds, pods, rocks fall in! Good thing I got out my old inspection mirror and had a look down there.
Its a good guess that these things are not good for the engine! I was amazed at the size of the debris that got in there. I am desnorkled but I am not sure how much of a difference it would make. I had to make up a vacum tool to get it all out..
I was delaying making up a mesh grill for the intake but not anymore. I would think it would resist a certain amount of debris.
Gentlemen, I recommend that you check the clean side of your air boxes with a mirror after a filter change, and mount some mesh behind the intake vanes.