Excellent story and write-up! Your car is beautiful, and if I had a Z4, I would want the exterior to look identical! The new-style Alpina wheels, the Alpina front lip that not-so-subtly proclaims your car to be among the most elite of roadsters, the beefy quad-exhaust that surely sounds like the war between Heaven and Hell is shooting out your exhaust pipes, and the aggressive (but probably fairly comfortably-riding) look of the suspension; they all come together to make the car straddle "the line" between "sleeper" and "exotic roadster" more and better than any other car. For fanatics who know what it is, it's drool-worthy and would be just as neck-snapping as a Ferrari passing by. To a regular person, however, it's just a nice looking Z4, maybe to be confused with an M Roadster.
I'll bet that thing has got some torque already, along with an engine that loves to scream all the way to redline. Bored/stroked to 3.35L must really change the engine characteristics. Typically it's done to give more low-end grunt, but looking at a dyno chart for the same model as yours (not the same mods, obviously), it also made it into quite a screamer. Your car is a perfect example of the kind of engine best-suited for ESS's Twin-Screw superchargers; you already have a great power/torque-curve, it doesn't seem to be extremely high compression so boost can be safely used, and the wide-wheels, limited-slip differential, big-brake kit, and suspension modifications mean that your car already has a perfect chassis for adding more power. Seeing as the twin-screw reaches full-boost around, what, 2000rpm(?), your car will find that it will have gargantuan amounts of torque available at less-than-cruising RPM's, and that it will continue on even past your "stock" peak-power point. In fact, the supercharger should mean that you will experience a continual increase in power, all the way to redline, even past the 6800rpm "power peak". You should have peak-power at whatever your new redline is. If you're making 300hp now, you can probably expect 420-450hp EASY from an ESS kit; and that would be like having 500-530hp from a centrifugal supercharger since you have full-boost all the time and are making MUCH more low-end power.
Good luck with the project. It's straight up BAD ASZ!!