It is the contributing factor to the increased 240 to 260 hp rating in the new Grand Prix.
It has larger less restrictive outlet port.
It requires 13% less power to spin. Part of the decrease in friction comes from a new powdercoating which replaces the previous epoxy coating.
And this new 3800 SC engine is now tuned to run on 87 octane fuel.
The blower is the only reason the new GP makes more power. All the other crap they added to the engine (computer controlled throttle and things like that) didn't help the horsepower any.
The blower requires 13% less power to spin and is something like 22% more efficient (I don't have the exact number in front of my face right now), so that means you can run more boost with lower temps, which means less knock, and more power.
The engine is not tuned to run 87 octane fuel, they now say you can run it so the negative of the premium gas isn't included in the reviews and so people don't not buy it because it requires premium, if you read into it a little more you will see that they recommend premium for optimum performance (I took this to mean that you will get knock retard on regular gas), just like you can run 87 octane fuel in a Series II L67, but you will just get some KR that you wouldn't get with premium, it is the same way with the Series III'*.
But, the blowers from what I have heard are awesome, and I am sure that sometime in the near future there will be a conversion kit for the series II'*, if not, I guess some people will be ordering the whole top end of the Series III'* engine, because since they didn't change the block or heads, the intake manifold should bolt right on, so everything will fit, you will just need an adaptor plate to be able to run the Series II Throttle Body so you have throttle linkage, unless it bolts right up to it, which I highly doubt.