I have a K&N on the Go-Ped and one in the M3, but from what I have read since I put it in the M3 years ago, I do not think I would go that route again. The K&Ns do not do well in head to head tests with paper filters. I have not had any issue over 10 years and nearly 200 track days in the M3 so I have nothing to complain about except you do need to have the car out of service for 24 hours to clean/oil the filter. To do it right, you use low pressure water flowing in the opposite direction of the intended airflow to wash out the cleaning solution. Once it is clean, allow it to air dry - no heat or compressed air. Then oil lightly and wait several hours. Reapply to the white areas of the gauze. It does look cool on the Go-Ped.
