anyone use or make forced cold air

Has anyone used or made there own forced cold air intake? if so what was the differnce in gas mileage and performance.

I rigged one up on my car. I took the air resonator out and routed the intake to the bottom of the front bumper cover. Used the stock filter and housings. A funny thing happened. I got an increase in power, but my mileage dropped by 5 mpg. from 44 to 39. I'm thinking the Mass Air Flow sensor and the Air Temperature Sensor sent word to the computer to richen the mixture because it was getting more air and colder air. I took it off cause of the bad mileage. I made mine out of some 2 1/2 inch flexible air hose reinforced with wire and a tin can cut out on both ends. Had to cut a hole in the sheet metal to get it to the front end. Have since plugged that back up. I did all this last winter. I don't know how it would work in the summertime with warmer air temperatures. Anyway, it was something to do.