The wiring is driving me mad.
Spent hours searching for the drain today. Strip the SC loom back and traced each wire. I narrowed the problem down to both the white wire and the purple&blue wire on the relay module, which were both permanent live. The white wire runs to the throttle position sensor and to each injector all of which were receiving 12v. The purple blue wire ran to the lambda sensor. Turns out that was the drain (the lambda heater).
So the issue is obviously the relays being energized and supplying the lamda heater. the white wire may also be the same issue. So apart from these two wires there are 3 thicker brown wires running to the relay pack which are permanent 12v. These I assume are energizing various coils inside the relay pack. I will trace these back tomorrow. but I think they all run to the starter solenoid positive stud. I now wonder if this should be a switched feed?
it is definitely an issue with something on the SC loom as i made sure everything lease was disconnected.