A good read:

http://www.edmunds.com/insideline/do...hotopanel..2.*

What a dramatic difference an air filter can cause... wow

 

interesting

 

I read this article before, very baffling how a little flutter can cause such huge problems. Gives one a good reason to replace a stock airbox with a cone filter

 

i want to see the graphs side by side or overlayed. Thats a nice jump in hp.

 

why would you be surprised by this. good example would be the K&N typhoons that look like high quality filter but runs like crap w/ throwing maf signals all over the place.

 

I actually had a similar experience with my ’03 Evo 8. It started feeling slow and did not rev cleanly up to red line. This was around 29,000 mile on the odo. After replacing the air filter with a new one there was a noticeable and significant difference. YMMV and I can’t back this up with a dyno, but I would say if you have a stock air filter, don’t go with the recommended replacement at 30K, do it sooner. I’m going to replace the next one after 20k. And I don’t drive dirt roads, this is normal city driving.

 

Must be an "Evo thing." AEM does the same for STis/STIs. K&N Typhoons work well with Subarus....

But, then again, some cars are just different. No car is the same. It may not work on yours, but may work on someone else's.

 

Well the K&N typhoon's problem is more in the piping itself and not the filter. There's a moon shaped piece that actually disrupts the airflow through the tube.