The easiest way to tell the difference between a GEN1 or GEN2 and the current GEN3 engine is by the selector plate. On a GEN3 the selector
plate is black in color and is the same design as an AEG selector plate
so that it slides in tracks along the top and bottom of the plate. The
GEN1 and GEN2 V2 engines had a blue selector plate that is secured to
the engine with a round bushing in the center of the plate.
The main difference between a GEN1 and GEN2 engine is the electronics. A
GEN1 engine will have 6 wires in the harness and each wire plugs into
the FCU individually while a GEN2 will have 5 and are all contained
within a single white connector that plugs into the FCU.