Anyone who watches NASCAR will be very familiar with the new Airhog air filter from the commercial they play at least 20 times per race, it seems. Anyhow, it looks like the same principle that the K & M filters use, and seeing the price is comparative, I would assume that the claimed power gains are similiar. Has anyone out there tried the Airhog or K & M filters? Before spending the $50, would it help “Bruiser”, my Mazda B2300 that I commute in everyday and frequently tow the pop-up with? I know…“It’s a 4 cylinder and it tows?”. I get that question alot, but it does pretty well considering. I was hoping the potential incremental gains from the filter might help enough to notice.
If you’ve got an unclogged paper filter it’s not likely you’re going to gain much that is measureable, particularly at part throttle. Most modern engines have fuel flow determined by an airflow sensor. Say you decrease the filter resistance so you ger more airflow. That means more fuel flow, that means more power. Unfortunately you won’t need it at cruise where you do most of your driving so you automatically compensate by using a lower throttle setting. You’re back to the same air and fuel flow. Any big differences might only be seen at full throttle. I’m not saying there will be no gain, just don’t expect miracles.
Here’s what you can do. Remove the air filter that your car has now and take your car for a short ride. If you notice any difference in performance (apart from the increased noise 
), then you might benefit from a free-flow filter. But in my experience, this is highly unlikely. At best it will add 1-3 hp to your engine. That is too little to get noticed.
On the other hand, these filters can be cleaned and re-used, so you will probably save some bucks in the long run. And they claim that they can trap more dust particles than an OEM filter.