Wow, that's some deal there...
While I can appreciate the function of this mod, and in a diesel, it probably makes sense, since the rpm range on one is very small compared to a gas engine.
In my case, I've become so accustomed to the shift patterns of my truck, that I can tell what's going on pretty much by feel now... Then, it only takes a second to blip the gas to check the tach since I'm already looking there anyway!
My vote is to leave the wiring harness alone and I don't even like the idea of a tuner, so that'll tell you where my 'conservative' mind is!!
But more power to those that have the gumption to do this kind of stuff!
Mitch