i'm using the ori stock air filter box, with k&n drop-in (RM270). the cai hose is 3", get it from ZTH forumer - ninja_jga @ Stanley.
it's a diy project so you need to look around on how to remove the stock cai (snorkel). there's a hole under the snorkel, where it's connected to another box... i remove this also. the hole need to be made bigger to accomodate the 3" cai.
...again it's a diy, need to be a bit creative.
good luck!:shades_smile: