Theoretical top speed for a R32 GTR is about 250km/h. Don't need a rocket scientist to figure out that a RB26DETT has more torque than a B16A engine. I don't care what aerodynamic coefficent a Intergra is it'll never reach 250km/h (unless a tornado is blowing wind in the right direction and plumetting down to earth from orbit, YES, it may reach 280km/h).
Just cause the speedo says, doesn't mean it can do!