You guy's are missing a big fat red sign here...
In ecomodding, better eairflow means better mileage... In engine tuning, better airflow deas NOT, I repeat, NOT equal better mileage... I'm a gearhead by nature and yes, I do have a flowbench and dyno out in the garage...
I can tell you from personal experience that getting better airflow in that K&N will decrease the mileage regardless of the other antics that rag pulled...
The computer will "solve" the problem by throwing more fuel in there to keep the car running the right mixture... More flow = more fuel = more power... Not mileage...
They can claim whatever they want... I'm not sold...
The reason why K&N does NOT claim better mileage is that the result of the K&N filter is more power, and since the driver will then 9 times out of 10 use that power that equals less mileage, even less than the actual change to the mileage had the usage remained the same...