You can believe the claims if you like, but you won't get 2 mpg better, especially when towing. I have very detailed records on a 2001 F150 Ford with a 5.4L, and a K&N filter got me about 1/2 mile to the gallon, on the road. Nothing in town. Acceleration was improved, and you have know how to clean and re-oil your filter so you don't contaminate the maf sensor as stated in post #2.
I also added added a "cat back" duel exhaust, matched the throttle body to the intake, and a few other tweaks. The K&N, made the only change in mileage. This was running the same 150 mile trip, (75 mile trip one way), every Wednesday, same time of day and traffic, for over 2 years. 50 miles of highway, and 25 miles of mountain road, going from 700 feet above sea level to over 3000 feet above sea level.
2012 Ford F250 ext. Cab 4x4
2002 Jeep Wrangler Sahara
2008 Yamaha V-Star 650 Classic
2008 Work and Play 18LT