^^The interesting thing about the intakes of the Ford trucks is that they all use the same parts regardless of engine displacement. I've checked, and the part numbers for the plenum, the tube, the airbox, the airbox lid, the snorkel, and the filter are all the same, except that there's a minor difference for the EcoBoost engines. That means that our heavy breathing 6.2L engines are sucking air through the same intake as are the six cylinders. Parts commonality is good for Ford - it saves them money. It's probably fine for the smaller engines, too.
But, it's probably not the best thing for our big high performance V8 power plants. That's a safe assumption, I think. But now, let's get precise. Where in the power band would a restriction in the intake system make any difference? At large throttle openings, of course, when the engine is sucking air as fast as it can get it. This is absolutely critical for a race truck that spends much of its time at wide open throttle, but how often are you at wide open throttle? For me, not ever. My Raptor is my daily driver and I don't like tickets or single-digit fuel economy. So the only thing my AIRAID system did for me was eliminate the hesitation I had when I abruptly called for more power as when doing a passing maneuver. I like that. That's why I bought it. But I had no illusion about increases in fuel economy, and realized none.
As for the inside diameter of the tube, in order for an aftermarket intake to reuse the factory airflow sensor and be compatible with the factory engine map, the diameter of the aftermarket tube at the airflow sensor has to be very, very close to that of the factory tube. If the aftermarket tube was bigger, the air velocity at the sensor would be slower and the ECU would be fooled into thinking that less air was moving through the tube. The result would be erroneous fuel metering and a strong tendency to run a lean mixture - very bad for the engine and for drivability.