I confirm this statement. This is valid for the EFI harness B4011-31P61 for example, which is an alternative part # for EFI harness 1990-91. Nissan did that to save costs. The harness runs only one wire (W/B color) from pin 58 to F23/E10 plug and injectors are connected to it in the middle of it as described in the post above. I didn't want to dismantle the harness in the middle. Here's the method for this new type of harness: _F23/E10 plug side: remove the W/B pin from the female plug, this wire becomes the switched injector wire. This step is very important because it isolates the switched 12V from the unswitched 12V (originally W/B color). _ECU bundle side: open the black bundle of wires and identify the wires of pin 45 (B/R) and pin 58 (W/B). Expose the splicings by removing the adhesive wrap. Cut the W/B wire (58) where the splicing is located. Find an unswitched constant 12V source and weld it to the wire which goes the pin 58 in ECU. Weld the remaining W/B thick wire to the splicing of B/R wire (45). Isolate the exposed wires with thermo sleeves.
Job is done, you have a 12V switched to power the injectors.