Easiest +12v ignition feed for Emerald ECU?

[tower]

Really would appreciate some electrical help from someone.
I have a Volvo 760 B280E Auto. It did have LH 2.2 K-Jet with a distributor but Ive fitted aftermarket ecu (emerald) with a ford v6 coil pack so it is running the ignition and injection. The ecu has a constant +12v ignition wire and a ignition sensing +12v feed also, and you can wire them both together to only be powered once you switch on the ignition.

I wired these 2 wires where I thought was good (spliced onto the red/green wire by the injector relay under the bonnet). I had the coil pack powered by the blue wire which originally went into the coil. The engine starts and runs great like this and I can adjust the timing and the fuelling no problems.

PROBLEM IS: Key-off and the engine keeps running until the fuel pressure goes so low that the engine stalls. E.g the in-place volvo ecu shuts down the fuel pumps but it seems the emeral controlled injectors keep firing and/or the ford coil pack keeps the plugs sparking.

IF I know which colour wire I can splice off so it all shuts down at key off then I think all be well. Suggestions and feedback appreciated! I have a haynes Volvo manual with wiring diagram but Ive clearly guessed wrong and dont fancy guessing a second time.