They're not "weak links". The car is produced to hold together as-is... not to hold together when you throw a nitrous shot or supercharger on it. Certain things can take more abuse than others - that's a given... but calling a part "weak" because it couldn't hold up to the mods is pretty unfair. If you don't want stock parts to break, then either don't mod, or don't leave the stock parts on.
But anyway... yes, the drivetrain has indeed been upgraded to withstand the extra HP from the factory. If you want to push the LS7 to 600+ HP, then you still may need to do some work, I don't know... but I am sure the tuners will find out.
