Review on Enhance Your 2003-2004 TOYOTA 4 Runner's Performance with K&N Cold Air Intake Kit: Increase Horsepower with 63-9022 Compatibility! by Eric Jenkins

I've been installing it for several years now. Have you noticed a huge increase in performance? (I think 13hp is claimed). Not sure. I figured the extra power would make me not pedal as it's hard to move, thus saving gas. More power + better fuel economy = win/win. How much did I notice in both cases? Not really. Maybe 1 MPG is better. at least after the first full tanks. (You ask why after the first few full tanks?). because it sounds cool and I'm stepping on the gas harder than ever just to hear it! I liked the deeper, hoarse sound. I was nervous I was going to have grunts, and even more nervous that the noise would increase at highway speeds. But that's not so unless you're stepping on the pedal to pass someone. I was happy to find that the depth only happens when accelerating and not at cruising speed.