The PCIIIr has a connector for the timing pulse generator (red connector near alternator) due to the PCIIIr's ability to alter ignition advance.
The PCIIIUSB doesn't use that connection.
They both use similar gray connectors and ground wire.
Otherwise they are similar in installation.
If you do decide to switch from PCIIIr to PCIIIUSB, if you bought the USB to Serial converter cable, you can download and save your existing map, then use the software to convert and upload the old map to your PCIIIUSB without having to re-dyno the bike.
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