As already posted, the stock air intake is by FAR a superior air intake than the aftermarket "cold air" intakes. The stock system IS a cold air intake, and will actually introduce more COLD air into the engine than those aftermarket "cold air" systems. The aftermarket systems get the air from under the hood, which is NOT cold. The stock system gets the air from in front of the truck, which is as cold as its going to get.
The filter in the stock system was designed to protect your turbo and your engine and give plenty of flow.
The size of the stock filter is that big because of how the air is actually filtered. The air actually goes sideways through the filtering media. That leaves an ENORMOUS amount of surface area for the air to pass through, since the filtering media is spaced closely together in channels down the length of the filter. The K&N style filters will stop rocks, sticks and most small animals from getting sucked in and not much else.
Those K&N style filters may be OK for normally aspirated engines, but belong nowhere near a forced induction engine. The turbo will suck the oil (that the K&N relies on for filtration) right out of the filter in very little time. That will leave you with little to NO filtering of air.
The stock filter can hold a few POUNDS of dust and still allow plenty of air flow to support the breathing of this engine.
Save your cash for the proper gauges you need for this engine.