Another idea is just to maximize the efficiency of the stock plenum. I'm almost completely done porting and polishing mine, by taking flapper wheels and a flexible bit holder to get where hands and even a 7 or so inch drill bit extension won't get. I've got at/ to about 95 percent of the inside, which is saying a lot, since it is difficult to get in there.
One thing that I noticed was that the air bypass port area is pretty restricted......not sure this would have much effect on any boost, since the bypass blade closes, but one would think that reducing restriction anywhere would have some sort of small effect at any vacuum/ throttle level.
One thing that I'd noticed on the plenum area on the upper portion of the port at the supercharger, the air has to negotiate a 90 degree angle. I was thinking of bevelling it and rounding that area so that the air coming from that direction would have an easier time entering the supercharger port. After porting my Mustang heads, getting into short side and long side radiuses in the ports, you get into the mathematics of air......it is lazy and wants to take the path of least resistance. In heads, at lower valve lift (higher pressure), air wants to take a short side radius, and at higher valve lifts (lower pressure), it takes the long side radius. Though i'm not exactly sure how the exact pattern is in which the supercharger draws in it's airflow at various pressures and psi's, easing the transition from the plenum to the supercharger port would obviously be a good idea.
Think about velocity stacks on an engine--the bell at the mouth, and then it funnels down to something smaller, which creates velocity/ pressure. Velocity is what is desired.....not necessarily flow. Looking at the stock plenum, what is a hindrance is all of the tubes that run off of the plenum......they have big areas where they siphon resources off of the plenum, whereas I think that they probably could have been mounted/ created/ drilled flush with the plenum so that there's way less turbulence.
One thing about the air bypass area is that if--in the transition out of N/A non boosted power to when the bypass valve closes to boost the system--if the supercharger can draw/ siphon from that air bypass area right before it closes, it's relatively close to the supercharger. It looks like there was a 1/8" or so step down from the plenum area to the bypass valve throat, which I initially suspected that Ford put there to prevent air reversion from the N/A vacuum system to the boost, but then again, it may just be a casting flaw/ mismatch from the factory. But here's the thing......if reversion is the case, then I'd think that you want reversion, because when the engine is losing manifold vacuum and going into boost in a fraction of a second, i'd think that any air resources available in the plenum area would be a good thing.
The way i'm considering the air bypass valve, is that it's a secondary throttle body......closed when in boost, but open at N/A non boosted times.
Can anyone post pictures of the air bypass throat area on an MP supercharger? I'm curious to see if it has any 1/8" or so step in it.