I do not know the real reason the factory does this, I can only take some guesses, but I have seen restrictive air cleaner inlets on many vehicles over the years. It has the effect of giving good (and quiet) performance right up until maximum speed, and then it generally enriches the mixture to limit power and speed. A diesel rental van that I had was so bad you could not use passing gear at highway speeds, it would slow down. You had to back off the accelerator and let it upshift to gain speed. This 86 E350 had a restrictor spot welded (from the factory) inside the air cleaner. Remove it and WOW.
My guess is that it is a factory move to protect engines from full throttle damage at full load, high speeds and long duration use. Better for the engine to go rich and reduce power than burn up. The inlets in most cases including the Blaster show a careful calculated design to be very close to the carb sizing. In the case of the rental van (which I bought and owned by-the-way) you quickly learned to back off the throttle on the highway.
Most of the factory inlet baffles I have seen also had a significant effect of reducing inlet noise. This has the double effect of increasing the perceived power boost because you have an intake howl to go with a modest power gain.
The effect of a carefully designed restrictive inlet is a WOT fuel mixture curve that is lean(ish) up through the curve until maximum rpm, then richens considerably.
Maybe also this is the manufacturers way protect against jetting inconsistencies?
I don't know for sure, just some speculation...
