The only way it would do anything really is if the stock one reduces air flow for noise. If you inhale lots, you have to exhale lots, so if there is no free flowing exhaust its not going to do much. More air, needs more fuel... ecu is only going to do so much. I would say exhaust/intake/tune for performance. Intake and or exhaust no tune is just for noise. Sent from my iPhone using Tapatalk