This was an early mod, and in my opinion, not really worth it. I used a hole saw and cut a 1 1/4" hole in the airbox and in the filter. A K&N to be accurate. I ride in the rain now and then and I also ride to work every chance I get, and there is a lot of dirt/dust where I work. Initially I noticed a slight improvement, but the increased gunk on the filter negated that in a short time. I plugged the hole with a 1 1/4" button plug and lived happily ever after.
