Thought I'd pass this along. I spent some time on it so hopefully others won't have to. The Greddy RPM signal adapter for the RX-8 is just a little black box with six wires ; four yellow, one brown, and one black. The diagram mislabels one of the yellow wires as red. Each of the four yellow wires taps into one of the four ignition channels coming out of the PCM. Black is just ground and I tapped that into the stock Greddy harness' ground wire. Brown then is the RPM signal output and can be wired right onto Greddy's stock harness, which also uses brown for the RPM wire.