the factory filter is contained in the filter box. the filter box has an intake hose coming from the dirty side the leads to a fresh air source, usually behind the headlight or from the fender well area. your factory ranger intake is the same way, drawing fresh, cold air from behind the passanger headlight.
most K&N kits change this effective setup to what i like to call a "warm air intake", due to using an exposed K&N filter inside the engine compartment. some kits include some baffles and shields to attempt to isolate the filter element from the engine compartment, but its still an exposed element inside the engine bay...which is not as effective as the factory filter that is completely sealed off from the warm engine compartment air.