According to what I remember from the instruction, the encoder and control box had to match serial numbers to work correctly, supposedly because they had a boost curve learning feature that made it respond faster with better control of the boost than the solenoid valves of the times. Since I'm out of the states and don't have access to the instructions, Google hks evc ez for the instructions. All it had on the control box was a power button and a knob, no numbers or anything.