I'm assuming that the surface area of the filter element is greater than that of the stock filter (i.e., less resistance). It's sort of like the reason why the small intestine has microscopic fingerlike projections--to increase surface area. The large volume of space within the heat shield probably minimizes air resistance when the engine needs it. Cold air is more dense, and provides more O2 for combustion with fuel, hence more HP. I got a kick after I installed the CF front air vents that are positioned in front of the radiator. Not sure it came out too clearly in the video, but you can see how they extend downward so that air entering the kidney grilles is actually scooped into the air intake. Real cool design. I also like the fact that if I can figure out a way to duct air through the driver's side front fender well (plastic), perhaps through the brake duct, I might be able to get more cold air in there. Of course, I can always remove the left headlight. Heh.
To be honest, I would have been happy had the shield been made out of plastic, and had saved me 500 bucks or so. I was so worried I might scratch the CF.