I read somewhere that the wire splice just tricks it into thinking it never gets out of third gear, effectively remapping 4,5,6 to 3rd. The M-Max box does the same thing, or something very similar I think. I've heard that the HRC and KISS boxes remap every gear differently, e.g. advancing the timing slightly.
Not sure where I read all this, but it's just off the top of my head, so don't shoot me if I'm wrong.
J
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MC28 SE -sold-
MC21 with RS250 engine -for sale-
MC21 race bike -soon for sale-