The M-Max removed the ignition retard for 4th, 5th and 6th gear (this limted the power for these three gears, which basically limits the overall speed capabilities).

The GPS wire splice goes one step further and maps the 4th, 5th and 6th gear into a more agressive ignition timing map, providing you with even greater power in these gears, which means more speed.

So technically the M-Max box does derestrict the speed limit, but doesn't provide you with the potential that the GPS ignition remap provides you.