The original II model altered the sensors to the stock ECU to make changes to the Fuel. The III model actually intercepted the signals to the Fuel injectors and manipulated the fuel directly. The IIIR also adds timing mods. The PCII only existed for a brief while on the 12.
You sure about that, Easy?? I think if you check with Dynojet you'll find that there have only been PCIII and PCIIIr models for the ZX-12R. There were some Power Commanders sold for the 12R that were labeled as PCII, but they were really PCIII units and had the wrong label!!
ALL Power Commanders for the 12 are based on the PCIII technology. Some where labeled as PCII's back before we decided to call our NEW Power Commanders PCIII's. There has never been a Sensor Offset (PCII type) Power Commander for the 12.