Did it? All I heard was that it had certain components hand-built and customized to each other (like the engine and the transmission). However, this is an entirely mechanical issue: since it wasn't really mass-produced, each motor and gearbox is different, so replacing them is going to be nontrivial.

Of course, I'm not an expert, and could certainly be missing information on other components of the GT-R. Either way, it's useful to keep in mind that the GT-R is a really crazy car :P.

I know they were trying to prevent it from being "chipped", and putting cryptographic interlocks in major components is the best way to keep the ECU from being completely replaced.