K&N air filters aren't designed for these small nitro powerplants (although they are often marketed as such) and will reduce the life of the engine as a result - the cause being that they allow finer particles through which oiled foam filters trap. If you're after something a bit better than the stock filter look for a slightly larger foam filter, ideally with two elements
You shouldn't need a cooling fan, a properly tuned engine with adequate ventilation (2in diameter holes in both the front and rear windows) shouldn't overheat. As you're drifting the car it may also help to remove part of the side windows so that air is forced over the cooling head when the car is sideways...