What are the major differences between the 997 Turbo and the 997 GT2?
o Engine HP difference
o 2WD vs. 4WD
o Standard PCCBs & LSD
o Race Seats
o Lighter
o Minor body styling
o Production # / Price, lol

Anything else significant?

Overhauled adjustable suspension
Clutch + flywheel
Tighter steering rack

The suspensions while basically the same are also completely different. As noted above the GT2 is completely adjustable, the TT fixed. All of the pick up points and bushings are different, solid vs rubber etc. All in all it gives the GT2 a totally different driving feel. The good thing is a lot, not all, can be gotten back on the TT with a few suspension upgrades. Add an exhaust and a chip and you're good to go.

Wider wheels, rolled fenders, aerokit, titanium exhaust, gearbox cooler, reinforce syncros, to name just a few.