[statik]

Looking at step 4, It seems you need to connect this to 3 wires on the hicas ecu. A and B just get spliced into the existing wires, C you cut at the hicas ecu, both ends now connect to the RSD, which appears to interrupt/modify the signal sent, much like the SAFC does with the MAF input. Beginning of step 5 says s13 180sx and shows a picture of the hicas plug and which pins correspond to A, B and C when looking at the plug end.

If someone can translate the wire colors in section 4 at the RSD, you are good to go.