one thing that should be brought up that could mechanically reduce the HP for the 08s and newer is a little know fact about the emissions systems, on the 07 VVT's there was only 2 catalytic converter, one on each exhaust manifold. on the 08's a third cat was added after the flange under the car just before the resonator. this would cause an increased restriction in exhaust flow, how much i dont know but would in turn negativley effect the horsepower the car was capable of produceing however not being of too much effect to torque seeing as it seems backpressure is good for produceing torque while a free flowing exhaust is better for HP, the principle the GTR exhaust system is based around. feel free to add to or correct anything that may not be quite right but that is how i understand it.