A solenoid that gets activated when your pump turns on. This is because you will be plumbing the alky hose into an area of constant vacuum (after the throttle body). Julio sells these as well and all the adapters you will need. You must be careful with the solenoid when screwing in the brass fittings as the break very, very, very easily and at $40 a pop I dont know how many you want to buy. The solenoid keeps the motor from sucking the alcohol out of the tank. I dont know if razor's newer style pumps need these or not. I would probably install one to be on the safe side.
The solenoid goes inline after the pump but before the nozzle and I wired my solenoid to open with the red and black wires going to the pump from the alky controller.
Just my thoughts,
Jerry jr.