Did a bit of diagnosis on the car last night and after suspecting the alternator was fubar it turns out it's ok, as is the battery.

However, I never see any higher that 12.7v on my SECS monitor and I've got a big voltage drop between the battery to the ECU so I would hazard a guess that the issue is the live feed for the ECU that is defective somewhere. Want to have a look at this again tonight but before I do i wondered if someone can poin me in the direction of where the wire is routed etc, am I right in thinking it comes from the battery and goes through a multi plug on the bulhead in the engine bay? As luck would have it I ripped all the multi plugs out apart from one that has a thick red wire in it, I suspect it's this one that is causing the problem.

From the wiring diagram it looks like this is connected to the TPS and relays/fuse 20 and the fuel pump as well, just wondered if I am on the right track?