somehting to note if you have the Cooper is that if you replace the air box you lose the air feed from the front of the engine and all the air that is being sucked in via the cone filter is warm.
I have the K&N 57i Induction kit for my
MC and i had to get some flexi tubing to re instate some form of cold air feed from the inlet "mouth" to where the filter site in the empty space once filled with the air box.
sam