the additional resonator box helps promote better low engine speed and very high rpm flow... I have no dyno results to compare it, but even my friend noticed it when I installed mine when I still had my stock cams... top end power was increased but the low end wasn't noticable on the stock cams because they were designed for low end torque to begin with
right now, even with all the upgrades on my car, I can cruise on a flat road in 5th gear at 1500rpm without bogging
how it really works? it gets too technical, but as far as I could understand, it involves sound resonance that uses it as pressure waves (and inertia) to help promote flow... VICS is just an extremely basic working example of this, and adding the resonator (that the FS-ZE has) further broadens the effectiveness of this... a true working example of this engineering is the VRIS intake manifolds that are in all of Mazda's K engines (except the miller cycle), the JF-ZE, and JE-ZE... there is a SAE article floating around the net about the KL-ZE... searching "mazda VRIS" will normally find it... read it, it explains the concept well
while all of this fancy intake s*** isn't going to produce the ultimate power, we all have to keep in mind that 99% of us aren't driving dedicated race cars that see constant high rpms... so you can say this "compromise" works very well for the street and allows for usable power at any rpm range
when either the MP3 or FS-ZE intake manifolds are combined with a good set of cams (like what you are running), the VICS design really shines... using crappy cams like the stock ones makes you think the intake sucks when in fact the cams are so restrictive it holds back everything and only works best with the 626 intake
also, what's good about the MP3 intake is, its VICS butterflies are like the MSP's and FS-ZE ones... they aren't the same as the bad normal FS-DE intakes where they can rattle itself off... the MP3/MSP/FS-ZE VICS butterflies are installed through a slotted rod instead of sitting on top of it... this means the it is very secure (pics on toprotege)
oh and anyone who want to say the VICS intake doesn't make top end power is wrong... my car spins the tires at the low gears near redline, and also hits the governor hard!

I'm still waiting for a time slot to get it dyno'd