My 306 is fitted with "one of the later ones" - it only gives 90BHP instead of 92! It is fitted with a Lucas mechanical lift/injection pump. The fuel injection is basically controlled by the govenor within the pump and the accelerator cable. The only electrical connections are for the stop solenoid (goes back to the imobiliser), and cold start compensator.
If I remove the plunger from the stop solenoid, and disconnect the compensation device the thing will run and keep running, until I either stall it in gear or press the stop lever on the pump.
/John