Only data I could find was that it has a more efficient 5th generation eaton supercharger that puts the hp rating at 250 and torque the same at 280 ft-lbs.

I'll stick with modding the Series II for now.
I can't believe the difference the 3.4 pulley made
....and now that the climate is cold and wet....

Hey 2000, we all love that winter time boost. Keep it all year long with water injection

Id kill for a new GXP bonney, 4.4 v8 with RWD. If only they'd do a manual!

I'm glad GM is going back to RWD, so much better in performance.

There was a previous discussion about this.. and I'm under the influence that they still haven't resolved the issue of the intake head gasket problems though :?

I believe the main difference in the series 2 and 3 L67 engine hp ratings is that the supercharger on the series 3 has a different teflon coating on the inside, allowing it boost more efficiently. I wouldn't doubt if the exhaust was opened up a little bit to balance out the more efficient blower.

Lee

I wonder what the weight difference between the series I, II, III are

With an improved 3800 Series III engine lineup, Grand Prix is unrivaled in base-level performance. The base GT model achieves 200 hp, and the GTP model up to 250 hp (at press time), with a best-in-class 280 lb-ft of torque. The GTP’* 3800 Supercharged V6 provides instant acceleration and no waiting for the power when it comes to passing. A more efficient fifth-generation Eaton supercharger boosts horsepower by 10 horses over the previous models. In fact, Grand Prix’* “base” horsepower begins where some competitors’ top models end.

Another racing-inspired feature that is sure to spice up the driving experience is the all-new Formula One-style TAPshift (Touch Activated Power), which is standard on GTP with the Comp G package. Drivers can engage a paddle on the steering wheel and switch from the ease of an automatic transmission to the fun-to-drive quality of a manual. The system has the fastest fingertip shifting response in the industry and better simulates a manual driving experience than any other car.

A jet-inspired electronic throttle control system (ETC) completes the performance package with speed-based response, which keeps the car maneuverable at low speeds and in parking lots, but ready for quick action on the highway. It is standard on both Grand Prix models.

Hey
Do I detect a relocated MAF sensor just off of the airbox before the accordian tube :?:
And the front exhaust header does not look like cast iron

Yeah, that looks like an LS1 MAF. I wouldn't be surprised since it would cost less and would the Series III to make more HP but not torque because of that. And I noticed at the LA Auto show that GM has gone back to tubular rather than cast front exhaust manifold it seems to make up that extra HP. Seems we know where the bottlenecks are for 100% dont we? :P