Perrin Charge PipeReplace the restrictive OEM plastic charge pipe to increase horsepower and boost response with the PERRIN Charge Pipe for 2015+ WRX! Better Airflow The OEM charge pipe on the FA20 DIT engine is restrictive, narrows down in certain points, and has pleats that make for uneven airflow. The PERRIN Charge Pipe has a perfectly smooth interior, constant radii, and gradual bends, making for much more efficient air delivery. This all combines to increase