I just know I'm going to regret this.
So we have basically (I'm probably over simplifying) 3 camps here? I won't attempt to place all the various personalities in the camps. I think, if I'm close to being correct, that they will self populate.
Camp one: The engine is a simple air pump, ANYTHING restrictive in anyway in the intake tract has a negative impact on airflow at all rpms and thus hurts performance at all rpms. Even if camp one were to agree with the some of the theories of camp two in regards to reversion entrapment, it feels that the positives (trapping reversion if any) does not out weigh the negative of having restrictions in the intake in the first place. Camp one thinks that mostly the poor souls in camp two are being bamboozled by tall tale theories propagated by those with financial interests in leaving intake tract restrictions in place.
Camp two: At certain lower rpm ranges and air velocities, a restriction can help trap any reversion in the airflow that might be caused by (I'm
way out of my depth here) VVT allowing the intake valve being partially open during the piston up stroke and/or some wave theory type stuff that a reverse wave occurs in the intake tract when the moving air (because of it's inertia) hits the closed intake valve. Thus, because of the restriction (secondary flies) the reversion is at least partially trapped and slightly pressurizes the intact tract so that when the intake valve next opens more air fuel mix will enter the combustion chamber than would have done had the restriction not been in place. This camp two position is only valid at the lower rpms and agrees with what camp one is saying only at higher rpms.
Camp three: HUH?
(to start off the self population of camps, I'm in this one, in case it wasn't already obvious.)
Sometimes, those in camp one and camp two feel so strongly about their positions that they appear to not like one another and they say things that might get the thread locked for a bit. When in fact they actually do like one another much much more
than they like all those popcorn chompin', fence sittin', dummies in camp three.