the K&N one had a filter, air feed and fitting kit. mine also came with a rubber cover so you can cut a section out of the weather guard. i just removed it.
The kit costs about £50 and i've noticed if anything it will drag ur fuel economy down.
I'm sure some one will correct me but the way i see it is more air in the engine means it's running lean, because of this the ECU pumps more fuel in to compensate hence using more fuel
Is that right chaps?