Colder plugs do cool down more betwen the combustions. With the next combustion the plug is colder so to create an ignition the compresion needs to be a bit higher. With other words: a colder plug shifts the ignition to a later moment.
With a shifted ignition you will get more rpm but if you correct the ignition back by lowering the button head you will get more compression giving more power.
Speed is only fiction but a 130+km/h MRS4 is for real.