super easy mod for the airbox, the YZ takes more works as because its forward facing, when it gets deep, it packs solid super fast. on my 11, so same bike, i did the timberlsed prefilter with no foam. works good until it starts getting fluffy. once it got deep, i just took the outer wings and the back of the airbox off. so its just the main cage that mounts to the frame. this works killer in even handlebar deep pow. BUT, its louder then anything i have ever road before. you MUST wear good foam expanding earplugs when setup like this or you WILL lose hearing fast. its not loud to anyone else but becuase your ears have a direct shot at the open intake... its bad.
also, take out the backfire screen under the filter, it likes to ice up and freeze over = bad running bike.