good question.....we has been experience before.it will be depend to the installer how there do it. but the correct way is arm the alarm then the engine still running after just switch off by the timer.
I've tried 550cc injectors on RB20det (that means 6 units) with SAFC 1 blue screen, the car can still run, but it's too damn rich on fuel, even if everything is set to -50% and even with fuel regulator installed...