I think he's talking intake air velocity, in which case, (and forgive me for I am NO EXPERT),
The stock intake tapers between the MAF and the TB, which has the effect of increasing air velocity (Venturi effect).
A lot of aftermarket intake tubes use a big straight pipe instead, which gives you more volume (and therefore, peak, high rpm hp) but lower airspeed (and therefore, less torque at low rpm). So, low-end grunt is sacrificed for the sake of higher peak hp.
Now, on the GMK, I don't remember, but it goes with the short ram, which I can't recall whether it's tapered or not...
And furthermore, in lengthening the intake tube, you introduce other factors...
And in locating the filter outside the engine bay, perhaps you counteract some losses incurred in other parts of the system...
At any rate, the measured benefits of the GMK are known, and every car is different, and so on...
Again, not my best subject, but I think he's conceptually on track, but there's a lot of other stuff going on specific to this engine in this car with this CAI that results in overall a very good system.
