The G6 interior parts look like they come from the Vibe and not the GP.

Just an observation.

http://www.pontiac.com/g6/specs.jsp?brand=g6&pagename=models_prices

I don't see a HP upgrade from the V6 to the GT or am I blind?

No herc your vision is straight on. Same HP. The GTP is claimed to be a 3.9 pushrod? DOCH? i have heard both doubt the second one. It is 250 250 hp/trq.........that is whati have heard also a 6spd tranny is supposed to be available. im laughing at that one!!!!

Same engine, but somehow mysteriously the GT gets lower gas mileage. The highway mileage bothers me, 4-mpg less for the GT and it's still the same damm engine!

The GT is probably a bit heavier, It has 17" rims vs 16" and wider tires. The tranny has a manual autostick so the ratios might be shorter for the GT. all those would help contribute to lower mileage.

I agree. 4 mpg average could easily be lost in even a different model of tire, let alone size, gear ratio, weight, overall wheel diameter, etc etc. Everything else on the car basically has more to do than just the engine itself.

Don't forget about that useless spoiler they are adding in only adds extra weight and drag. And the biggest contributer to the loss of MPG is the tire size.

The 235/50/17s I have on my GTP cost me at least 1-2mpg highway over the lightweight 16" torque stars.