I ran a K&N w/Outerwear in a stock airbox for months and did not have to re-jet and it seemed to do fine in the dirt. I have used the stock filter, Ready Filters, No-Toil, and K&N and have good luck with all of them. For really dusty conditions I am going to try a Filter Skin over my K&N and see how that works as I do not want to spend the money to have mulitple Outerwears. If I had the money or time when I bought my foam filters then I would have bought Twin Air as I believe they make an excellent product. My instincts were to not use a K&N but when my filter died the night before going on a riding trip and the next morning the only thing I could find was a K&N and Outerwear. The builder that I got it from said that it would be fine in dusty conditions and it has been so far. I think that any of the foam filters will work fine for you and if you are using the stock airbox without anyother changes to the engine you will not need to re-jet.