What possessed Suzuki to use an oiled foam air filter on the Burgman AN400 when a paper element is clearly a better filter medium, and virtually no street bikes use oiled foam OEM, AFAICT?
Additionally the oiled foam medium runs the risk of having sensitive parts of the EFI intake tract coated with oil, and perhaps causing problems. Also a simple replaceable paper medium is faster and more convenient.
Check out this link if you do not believe that oiled elements are inferior.
Air Filtration and Flow Test