well i have a k and n replacement filter in mine and havn't had any problems with it. two days ago i was playin around with a cone filter and some pipe and fabbed up a temporary intake cuz i was bored,lol. makes the magnaflow exhaust on my car sound 3times louder, its crazy. but i just put my box back in because the intake i made wasnt very pretty. ill make a nicer one someother time.