I read an Off-Road magazine article a few years ago about a Ford 1-ton Crew Cab dually 4x4 with a 460 that they were trying every trick known to man to improve the gas mileage.
I believe they got it up to around 13 mpg from around 8 mpg. One of their tricks was to wrap the air intake duct with metal heat tape that supposedly helped keep the incoming air cooler.
A larger diameter metal tube, surrounded by some of that dryer heat vent foil tubing stuff would allow more air in, while keeping it cooler. Might look kinda' weird, though, with not any noticeable difference.

 

My 98 4.6 did not have the intake silencer, FYI.

 

My 2002 SCrew does not have the same setup as shown in the pictures. It isn't tapered like the part shown, it is smooth and the same diameter all the way through. I decided to leave mine alone, it looks better than the end result of the mod in the pictures. Frankly, other than the air box, the factory part looks better than most of the kits out there. It's smooth, the same diameter of the throttle body, and is insulated from heat.