The Big Sucker is engineered to give your engine maximum airflow, which means more horsepower, more torque, and overall improved performance. Dyno testing has shown the up to a 21 percent gain in horsepower from simply adding a Big Sucker kit to your V-twin engine. Stage 1 kits give the option to use either your OEM air cleaner cover or to install an Arlen Ness custom cover.