I have been reading here, thinking to do this air intake mod, as I have Arrow headers and ECU flash. In the Suzuki parts diagram, the part is called "seperator", not "restrictor" plate.
So the air enters from the bottom of the airbox and then goes through the seperator plate, then through the filter to the engine. As said before, wouldn't the filter itself act as a "diffusor" or seperator if the plate wasn't there? In all my thinking (no air flow engineer who really knows their sh t has chimed in here to explain why the plate is there), I would guess the plate is there to calm and slow the air down before it enters the filter, ie., calm the turbulence.
Earlier in this thread, it was shown that in the Z1000, the "diffusor" plate is perforated with holes. That makes sense. Calm the turbulence down, but let as much air as possible pass through.
So I am the first guy to suggest drilling multiple perforation holes in the plate, without removing it completely! Maximum calm air to pass through.
Unrestricting the frame air intake holes also makes sense. Maximum air in, maximum air out (with full aftermarket exhaust and ECU flash)
However, when I got my ECU flashed by Dano's. he asked me if I was going to keep the OEM air filter or replace with aftermarket. He said aftermarket gives "a couple of hp more", on Dyno, gains barely noticeable.
My conclusion: this mod might make the intake sound/noise more cool, but offers MINIMAL GAINS, but certainly gives me one more thing to tinker with this Sunday! Can't wait!
But then I think ... you know how close to ram air we have on this bike's intake system? The intake holes are already there in the frame allowing direct air entrance to the airbox ... I'm going to develop external "scoops" outside the plastics to the frame holes to pick up and force air into the airbox! The faster I go, the more air forced into the box. Now we're talkin'! GSXS with ram air!