I have managed to find a very large extra set of wires, all wrapped up nicely, with a huge multiconnector on one end going nowhere. It goes to the ECU on the other end. I assume it was for headlights etc on the Nissan 200 SX the engine came from. It has been in the way, so I cut out the wrapping and rewrapped the important wires (the ones that go to the injectors, sensors etc).

Where do I cut this thing off, and what do I do with the wire ends?

The engine runs fine without it.

Don't cut anything until you have checked a good wiring diagram and are sure they are not important, as you know wheretheu come from you should be able to find them easy enough on the diagram.

As far as cuttig them off, I use an insulated connector crimped on, and then wrap with insulating tape. Might be worth marking on what they are so if you find you do need it later you can find t and extend it back to full length.

Unless you're going to take the whole loom apart to remove the wire it's probably not worth it. A 8 foot length of wire weighs a bit, 2* 20cm bits isn't worth removing. I'd just leave it. Usefull incase you ever find you need it (even if it's just as an extra cable for some later addition)...

i'd leave it in and tape it to some other ones to keep it out the way

OK, thanks, I'll wrap it up again and coil it up. The problem is that I have very little room in the engine bay as it is. The Nissan wiring diagrams cannot be read by mortals. Have you checked a Japanese wiring diagram???