Interesting.
but when I calculate pressure loss of a sudden contraction from 80mm t0 64mm with 16300 l/min air (30degC) going through it (that's roughly the air my engine consumes at 6800rpm at about 8,5psi of boost, I calculate a 0.14 psi pressure drop.
So that's about 8 times more than your example.(which is probably the loss in a straight pipe)
Also a rough calculation though. from a german site that's all about pressure loss
http://www.druckverlust.de/
Interesting that you can calculate not only straight sections, but all kinds of situations.
(but all these calculations are rough estimates (more accurate data obviously comes from navier-stokes CFD calculations and the sorts), but a rough estimate always gives some sort of guideline)
Obviously you won't get huge gains from a bigger TB (otherwise it would be included in any FI kit), but as I said, it's a fun and really cheap mod as long as you dont spend big bucks at dinan and such. It's (I think) also possible with cheap used parts from the internet and some ingenuity and efford.
Just like intakes, headers etc people somtimes attribute huge gains (10-15hp and more) to such mods, and if multiple done, add those gains being under the impression that intake-TB-headers combo alone will give +50hp or such a ridiculous number....
Psychological HP's ...
(dyno guy: lets tweak the parameters a bit so that another happy customer leaves the building....)
As regarding to the preciseness of the pedal: I don't think that's a real problem. These differences are still quite small, and with the sports button it's also not a huge problem. Even with the twinscrew (which adds over half the horsepower!) it's not a real issue. With that the preciseness of the pedal obviously also is compromised as you regulate huge power.
So I don't worry about the accurate response. If I would, my car would have been undriveable a long time ago.
About the n54 intake manifold:
Very straight foreward. Just a plenum (fairly small btw) and some fairly short intake runners. No disavalving, resonance ducting etc etc whatsoever.
actually looks a bit like the ESS TS2 intake manifold (but that has charge cooling obviously)
The new m3/m4 also uses this manifold BTW.
Easy to fit TB's and stuff, but sadly not suitable form m54 (no injectors
)