I beleive it can with a fly by wire throttle if it wanted. Even if you are giving it more air, the FBW throttle can close a bit, to give the "normal" airflow. This is what I would guess it does when you install a popcharger.
With the plenum, as it is balancing the air to the cylinders rather than letting in more, it gives better fuel/air mixes across all cylinders, which means better burn which gives more power
Usual disclaimer applies, I could be talking cack
Likewise! Proves the point then - it is inconclusive.....
But there are quite a few people who have had their cars dyno'd with Injen kits on, and they showed an increase. One of the guys posted his graphs on here, and there are a few in the US too. Confusing!