I know alot of people have used the PVC pipe or Ghetto Fabbed as most call it with essentially the same effect as those of us who have spent the money on the High Dollar K&N, AirAid, etc units. I think the important thing is that if you create one, to use one that has the fewest twist and turns as possible. Use as many straight pipes as possible and don't use couplers any more than 45*.