"Another special model of the R34 GT-R is the M-spec. It was similar to the V-spec, but had special "Ripple control" dampers, revised suspension set up, stiffer rear sway bar and a leather interior with heated front seats. The 'M' on the M-Spec stood for Mizuno who is the chief engineer of Nissan." and it goes on to say "The V-spec II Nür is based on the regular V-spec II model, and the M-spec Nür was based on the regular M-spec model. Other than the addition of the Nür engine, the Nür models also included a different color of stitching on the interior trim, as well as a speedometer reading up to 300 km/h"
I didn't know there was an M-Spec either. I was only aware of the Nur until I saw this.