Just got down modding my airbox. Essentially it's just an "elbow removal", but I adapted slightly for a more finished look. Didn't do the deckplate mod yet, wasn't sure if I wanted to do something where I couldn't go back to stock if I needed to.
Started by picking up one of these from Lowes:
NDS 4" round grate/black - #52063 40011
and I had some of this laying around so I ended up using it as well:
Started by removing the airbox which consists of (3) 12mm bolts at the top/bottom/rear. You'll need a long extension to reach the one at the bottom. Disconnect the vacuum hose coming in to the side of the airbox from engine compartment side, and disconnect the electrical clip at the MAS. Remove the (2) 10mm bolts that secured the airbox to the inner fender well (where it connects to the elbow. Finally loosen the clamp that attaches the airflow hose to the MAS, and pull up and out on the airbox while using a twisting motion (its hard to describe but when your doing it you'll figure it out).
Next, I pulled off the passenger side wheel cover, and pulled back the black inner wheel well cover. I HATE THOSE LITTLE BLACK RETAINING CLIPS THEY USE TO SECURE THIS!!! I broke 2 in the process, but fortunately I had a few left over from when I was playing around with the driver side mocking up my mudflaps. Once my flaps go on I won't need a few of these anyway so I was able to swap these out. You also have to remove the 3 10mm screws that secure the wheel flare to the the underside of the fender. Once you get the cover pulled back, you can essentially reach up in there and wiggle out the elbow assembly. It consists of (2) pieces, the "back" piece which you pull out from the wheel well, and the "front" piece which is the part that attaches to the airbox, you pull out from the engine compartment side.
The inside diameter of the 4" plastic grate is approx. 3 5/8" while the outside diameter of the airbow where it connected to the elbow is only approx 3 1/2", this is where the stretch and seal tape comes into play. I cleaned the airbox with rubbing alcohol to remove any dirt/debris and wrapped the tape around the airbox opening, making several passes to build up the O.D. to 3 5/8". (This tape is approx. 1/16" thick, so it doesn't take to many layers to accomplish this). Once I measured/aligned everything up, I simply pushed it on the airbox opening, and made sure it was a snug fit.
That's essentially it, once your done with that just re-assemble, and take pics. It fits in there pretty snug, and I like that it still looks somewhat stock, and I could always just disassemble it quite easily if need be (which I might do when I do the deckplate mod so I get direct intake from only one location not from the front and the side.
When I do the ISR i'll probably mill the openings on the grate slightly just to maximize the air flow, however I feel more comfortable having some sort blocking in place in case it pulls in any sort of debris (ie a leaf, piece of paper, or plastic, etc...)
Well thats it, heres some pics.