Actually if anyone gets Car and Driver, this month they were talking about the huge difference between the 4 GTR's they have tested over the last couple of months. There is an article called "What is the GTR's real horsepower?" There was the first one they tested that everyone was like "OH SNAP" when it ran 0-60 in 3.1s, but in a comparison test in Aug. like two months later that ran 0-60 in 4.1s.
I wouldn't doubt that Nissan/Infiniti sent out a "magazine car" that had the boost turned up to give people an idea of what it was capable of.
Case and point...is the Nurburghring fast lap GTR's boost set at what it will be delivered to the people at? If not....it's just another variable then.