O.K. fikrst off Never use gas as a parts cleaner. If you need to use a solvent, use paint thinner, it does a good job, and doesn't have the vapors that could get you killed, or burn your house down.
As far as the filter, I have the K&N in the air box, using the Pro Design adaptor, which is a must, for an air tight fit. I also us the outerwear to keep the larger stuff off of the main filter.
I also use the K&N cleaner, just wash it off with water , and K&N oil. The combination works very good.