What a difference. The airbox is easily twice the size of the factory airbox. I have gained a little bit of mpg (about 0.5 mpg in the city, 0.9 mpg on highway driving). But the difference is the effortless of the acceleration. The engine runs smoothly and accelerates cleanly and doesn't feel clogged up or choke on hills. When I drive into the mountains is where this is most noticeable. I love it and it is worth the hour of installation. Thanks Jason!!!