I wonder if the improvement is due to the design of the intake and less to do with the oiled-rag filter itself. I removed the resonators from my stock Nissan intake and noticed a "seat of the pants" improvement, but no improvement at all with my K&N panel filter.
I dont need an oil analysis to determine whether or not my K&N panel filter is doing it's job. I used one for a couple of months and my oil turned very dark on the dipstick. I switched back to a paper fram (lots of pleats) and changed the oil. Funny how the oil now stays much lighter between...