are you converting a NA harness to turbo ??

1)the pressure reg might be listed in the workshop manuel ,when i did my wiring i checked the start of the wiring section out and found that it has a list of most the sensors and shows a picture of what they look like and tells you what they do ,maybe check there ?

2)you dont need to hook the nuetral start wire up ,i dont have mine hooked up and my motor starts and runs fine !

3)and yes the standard tacho will run of the tacho out put wire ,as it just goes to the coil pack trigger wire ,but it is joined in at the computer end of the harness (from memory)

4) you dont need to hook it up if you dont want to ,youll need to unhook it if you put a boost controller on it and the computer will work fine without it hooked up too

5) i wouldnt do anyhting with that wire ,it could blow something up if you power or earth it .just check the wiring diagrams out again ,theres about ten diagrams each with little bits of added info haha very misleading sometimes !

as for the o2 sensor you can use one of an sr or just a standard ca item aslong as the plug fits the nissan ones usualy work