I used a whole bunch of stuff. To enlarge the hole I used a mini-hack saw, cutting pilot holes with a large drill bit/ or hole saw. Then I smoothed the ridges inside the top of the air box with a rotary bit on an electric drill/ w extension. I only did the ones perpendicular to air flow. To smooth out the rough edges from the rotary bit, I used 60 grit sandpaper wrapped around an appropriate sized deep well socket. A dremel with the right options could do all of this.
Well if you do it like in the pictures a hacksaw or sawzall will do it in 30 seconds. I was fancy and wanted to make sure water was not a problem unless my truck was underwater. I also directed it for best cold air flow in both halves, not just gutting the bottom half of the box like in those pictures.
TOP HALF: There are cast- in plastic support ridges that form a criss-cross pattern in the upper air box. Some of these run perpendicular to air flow. I guessed that by removing these perpendicular ridges, especially those closest to the MAF, that volume and velocity of air MAY increase. It also reduces weight. Structural integrity is still maintained, as is filtering ability.
BOTTOM HALF: The side of the air box facing the front of the truck was removed. The ridges in the bottom half were contoured when possible, to smooth flow. There is a small hole right near the headlight support where cool air comes in. Thats the reason I only cut the front, and not the sides, like the picture shows. I don;t want hot air from the engine compartment feeding to the engine, and want max protection from splashing. The amount of dirt in the fender below the air box is amazing, and it was not just dust, it was pebbles and stuff. This is just my opinion and what I did. Its not right and its not wrong. Its just me.
thanks for the info guys. i just hacksawed half of the bottom of the box. left the other half on there as a heat shield. took sandpaper to smooth out the rough edges and hosed it off. definately noticed an increase in power. gained a nice engine sound when wide open too.