We like our K & N filter. We put a catback set of Flowmaster 40's on at the same time, so I don't know how much the CIA alone improves performance, but we're very pleased with the overall results. Highway mileage (5 speed) is around 28 mpg, which we also like.
Take it from me though, be sure to put that little screen door wire mesh thingee in the CIA assembly. You wouldn't think such a small part could have such a huge negative effect on your car's performance.
I agree, a CIA will make a much larger difference. I had a 2004 Jeep Grand Cherokee, and originally put a regular K&N Filter in it and didn't even notice the differance. A few months later I upgraded to the K&N CIA and the differance was huge. Got more throtle responce and it sounded better. I even notice an MPG gain of 2 MPG, and on an SUV that was huge.
I didn't even mes around this time and went straight for the CIA for the Stang.:bigthumbsup Get one you won't regret it.:gringreen
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