The pre-FAP bikes don't have a suitable vacuum take off point apparently. As I have a spare oiler I thought I would have an experiment. If you connect a small syringe to the vacuum connection of the oiler it only requires a small negative pressure to open the flow valve. Drilling a hole through the shaft of the syringe allows a pin to be inserted to "hold" the vacuum. Downside is you need to remember to switch on and off.