I use one. Not a K&N, but the BMC brand that Ducati includes in its air box kit. I don’t consider an air filter a performance item. More of a convenience item and a durability issue. Yes, online tests you can Google show paper filters flow as much air as an oil and gauze filter. The thing that some tests also show is paper filters flow less air as they become dirty where the oil and gauze filters keep flowing as much air as new. Something to do with how dirt collects in the oil rather than becoming embedded in the paper as I remember it. I clean mine at each valve check interval, which is probably more than it needs to be. I will "knock out the big chunks", if needed, whenever I lift the tank. It's also one less item to buy come maintenance time. Not sure what a paper filter costs for these bikes (never bought one), but buying them would likely wind up costing more than a K&N over the life of the bike if you ride a lot. I had one in my old SS for almost 48K and I have had the one in my current bike for almost 25K.
Comments keep coming up about poor filtration. People have coated their air boxes with oil and have said they find a lot of grit inside. This is proof positive to them that oil and gauze filters do not work as well as a paper filter and people should stay away from them. I have coated my air box with filter oil and did find some grit, but nothing I would consider a huge amount.
I do not mean to be challenging here, just genuinely curious. Also this will be the 3rd time I have asked this question in this forum on a thread like this.... No answer yet!
Has anyone run the same test (coating the in side of the air box with oil) and found less grit inside the air box while using a paper filter as compared to the gauze filter, proving at last, that paper filters do in fact filter better? This of course would have to be done in the same riding environment to be valid.
Use them, or don’t. I don’t think you can go wrong either way. Just be sure to not over oil the filter! I did that the first time I cleaned the filter on my old SS. I had filter oil dripping from the air box drain!