There's a guy on the BCMazda site that made these, "MicaGuy" is his login. I bought a gnd kit from him for $75cdn, installation included, which was basically the cost of the parts.
It included a new mains wire to the fuse block and alternator, plus a complete redo of the engine and specific sensor ground points. It's a really professional looking kit (I'll send pics if you want) & very well built.
Did it increase the hp? Probably not enough to be noticable, but I did notice that the engine seemed to run and rev a bit smoother afterwards.
Let me know if you want pics; I'll see if I can get the parts info from him.
Cheers,
John
Vancouver, BC