Who has built a cold air box?

I've never done this but if you cut a larger hole in the radiator support (larger than the small one it now has) you'll get some "ram air" effect to the air filter!! There's a lot of air pressure against the radiator support at 30/40/50 and 60 MPH. If you also enclose the filter space so that the only intake is from the hole in the radiator support you'll get even more ram air effect to your intake!!