K&N was real big in the diesel pickup world and people were putting them in left and right and getting great HP gains. Until they blew an engine and it was full of grit from the K&N being poorly maintained. 10K for a diesel engine VS HP gain. Was not worth the risk, so I pulled mine went back to a high quality paper filter.
Not sure about migrating oil to the MAF in the subaru, but is the risk worth it?
And this whole thread started by someone asking if it was ok to maintain the K&N filter, in a way that was not what K&N calls for. Due to a broken sprayer.
Your car you choose, Lots of info about them on the diesel pickup forums, and kind of like oil debates, no one really wins, and you can make a video to support any point, it is all up to You and the way You maintain or do not maintain the filter. And your risk/reward assessment.
Good points and options pointed out.