There are key differences between the stage one and two air cleaners. The main difference is the air intake. You receive more air intake into the engine than in stage one with stage two. Your stage one air cleaner is designed to capture larger particles. The stage two has been designed to capture smaller and more refined particles. With stage two, you will need to look at different upgrades as well. The first is the exhaust. It has to compensate for the increased volumes of air outlet.