I have to say I have had No trouble with the filter on my 7900 too the point I think I wasted money on a spare lol. I read this post last night Just got back from cutting some very dry pine mind you only ran two tanks through it but it is spotless. The out side of the saw is very dusty yes very sharp chain was making big chips but you still get lots of dust. The air box is even clean, dare I say Jred/Husky Clean.
I also did my good deed for the day by helping out another firewood cutter. Cutting on public land in the forestry on a Well Head road had another cutter pull up and say ah you got the good spot I told him tons of trees and the Dog would like some company as he had his Lab with him. He had a brand new MS 290 on it's Maiden Run. He forgot his Scrench and having a brand new truck no tools with him to adjust the new chain.So I lent him one of mine, after we cut are loads of wood he saw me pop of my top cover and have a look he asked what I was doing I told him so we had a Look at the Stihl and guess what No dust got by the filter either. Then I told him about AS, so next time we cross paths he will probably have a new MS460
P.S I told him don't get a fat ass 441 I also steered him to the Jred dealer too.