K&N air filter model 33-2036

I'm not sure this one changes anything. Maybe some street cred' or style points of some kind.

I think I hear the air whoosh in a bit more loudly, but it might be in my head.

Reference of the K&N filter is 33-2036, as found in some Caterham 420 racing regulation. Caterham themselves are not consistent with the one they ship when you order from them. So 33-2036 it is.

Perfect fit, just 6 screws to remove from the airbox, easy game. A long PH2 screwdriver is required.

It is pre-oiled, you just put it in there and close the lid.

For reference, the original paper filter was a Ford unit with part number 1 729 854

An alternative to the K&N is the P950366 from Green, a Ford Fiesta item (thanks, Guillaume).