I would say your gains are zero either way. The only thing it does it make your engine louderIf you look at our factory intake, its suction is inside the driver's wheel well, already pulling in cold air. As a matter of fact, the after market ones may reduce your performance since they take suction inside the engine bay!! If you were to drop a K&N factory replacement filter into the factory airbox, you would probably get the same effects, just not as loud. Only reason I got the Injen, it was on Ebay, no one else really had one...and it adds some bling under the hood. I already had a factory K&N drop in, so if it made a performance difference, other than sounding cool, I haven't noticed.