A good smooth pipe intake is far superior to any panel filter setup ive seen.
Most of the good brand filters out there have close performance when coupled with a good intake piping kit. Its more wise to have better intake piping than to argue just to argue about which filter is the best.
Reducing restriction at the end of the intake pipe also will improve air flow into the engine and increase power. You can do so by using a less restrictive filter with a smooth entry. Some filter have a built in velocity stack too. As I can seen dyno test to show that a a smooth entry will increase power and torque. eg a velocity stack at the end of an intake pipe for a race car will make more power than just having a pipe on its own.
Smooth piping will keep air velocity up.
Ive seen back to back dyno tests and its a matter of a (if memory serves me right) 10whp on a 400whp car.
Ive looked up the results to help you guys more.
This is purely an air filter test.
Intake remained constant and all that is changed was the filter kit and MAF adapter that comes with the filter.
These are just short ram intake there is no intake piping between the MAF and the air filter.
Notice the power at the rpm range of where peak torque is made.
One of the more restrictive filter which was the small half size cone K&N caused more knock so with a tune you cant run as much timing so you are restricted a lil because of the poor air filter choice on such a higher powered car.
Even a certain air filter kit will cause the air fuel ratio to be different.
So further ecu tuning will increase power gains.
So then improved intake piping and higher flowing air filter will improve power.
All you guys with all motor/naturally aspirated cars need everything you can get.
An intake kit can get you 5kwatw on average. You might not even feel that on the butt dyno but use a real dyno or take it to the drag strip and im sure you will see more power and faster times.