I can say that I feel much of a difference while driving, however, so far my gas mileage is better than it was, but I can be sure as to whether it's caused by the filter or by my driving style getting better. No power gain felt though, and there doesn't seem to be any noticeable change in intake sound.
Focus Fanatics Forum
Place of Install
Mileage at Install
I obtained this filter when I purchased a set of winter wheels off of a member of the Focus forum focusfanatics.com. When I picked up the wheels, the seller also gave me some odds and ends he had left from his focus which he had sold. The filter was clearly used so being a lifetime filter, I picked up a K&N recharge kit and it was good as new. Cleaning process was really simple and overall took maybe an hour and a half. Install was super easy, it took a little wiggling to get it to sit right so the cover could go on, but nothing difficult.