A K&N (and those green ones out there) air filter uses 4 ply media while the S&B uses 8 ply media. The problem with the K&N is that it does not flow more air than a good aftermarket filter. If you take like a Wix racing filter or any of the other performance dry filters they all flow roughly the same amount of air (enough to make the hp you're looking for). Now, if you take a stock replacement filter, yes, the K&N is going to flow better because the OEM filter is designed to stop everything, not make horsepower. The first time you use the K&N it does not stop as much dirt as the other filters, and every time you clean it that gets worse and worse. To the point that if you clean it 4 times it's just plain pathetic. (The S&B was withing .1% after the 4th cleaning compared to when new). The media actually tears allowing particles through. Here's something to think about too. It's not the particles you can see that the air filter is stopping. It's the stuff you can't see that's going to hurt the engine.