I didn't realize how well the OE intake works until changing the filters on my girlfriend's TRX the other day.
Felt a little bad having gone past 22,000 miles when the book says to change them at 20K, but was pleasantly surprised to find the "dirty" side being darn near as bright white as the intake side. Almost put the old ones back in.
Also, I don't see how a "cold air intake" could provide air that's any cooler than what the factory setup delivers. Besides, the claimed extra 21 hp and 41 ft-lbs. seem unrealistic. Any gains would likely be at the expense of efficient filtration.