The great thing about these Mmax boxes (KISS, POSH, HRC included) is that all the aforementioned companies made a fortune out of conning the paying public into buying a "wire splice in a box" as Granty puts it.
A simple wire splice all neatly wrapped up within the harness is a much better way of doing it, as the chances of ever wanting to undo this mod are zero.
But then again, as there's no ill effects then there's no harm in leaving it on there.
The GPS plugs (grey) do absolutely nothing. Just wires into and out of the box. Don't even bother to connect them.