[TTopJohn]

I have seen the Duramax test linked above, and others. And I haven't used a K&N in a while on account of being scared away from them by the internets. But personally, I think I'm going back to K&N, or whatever oiled gauze filter comes with the Volant airbox.

Maybe it doesn't stop as much dirt under certain test conditions and procedures, but it clearly flows better in all of these tests. And in the real world, I know too many engines that have run K&Ns for too many miles with zero failures or diminshed performance symptoms that could be attributed to a filter not filtering well enough. Maybe its because these cars are owned by persnickety folks who change their oil more often than necessary, but I fall into that category myself, so if that's the key then I am set.

Folks are fond of saying that the throttle is the only restriction that matters, so a freer flowing filter or a less restrictive air intake won't add power or efficiency. But I don't think this is true. I've seen too many performance increases, seat of the pants, dyno, and 1/4 mile, from decreasing other restrictions while leaving the same throttle body in place. Sure, you are leaving power on the table when you reduce certain restrictions but leave other restrictions in place. For example, on an LS1 Camaro, if I put a bigger cam in but leave the stock exhaust, I won't see the same hp and torque increase that I would if I put long tube headers on at the same time. But I will see a gain. Same as if I do it in reverse - put long tube headers on but leave the stock cam - there's definitely a gain, just not as big of a gain as if you did both.

It's not wrong to do it one way or the other, just understand what you are doing and pick the route that will accomplish your goals.