Apten has a dyno graph claiming a 21whp gain. JLT ram air claims between 16-20whp, and their cold air kit claims more. I dont know about K&N, and of course all of this is based on what a company says it did for them. Im still stock, maybe you wanna try some other sites....more related to SVT, with guys that have intakes for your answer. Svtperfomance.com, and modularfords.com. Oh, btw, it appears most of these cold air kits are using K&N filters.