Bigrick wrote: If they improved mileage and performance, wouldn't the manufacturer use them?
The manufacturer can't use them because it requires the owner to raise the hood, remove the air cleaner, and clean it. The average driver has no idea how to change the oil.
There is nothing wrong with K&N air filters. I have put them in a 1992, 1997, 2000, 2003, 2005, 2006 and a 2010 vehicles.