My guess is you have a big leak in the line going to the 3/2 valve, which is robbing you of vacuum in the line going to the ignition switch. You might try plugging that line and see if it shuts off with it plugged.
I guess you were in the process of cracking each line to the injectors to see if the smoke stopped when any of the cylinders were starved for fuel? Did you find a faulty cylinder, or did it smoke on throughout the process?
Good luck!