Writing this just to document my findings and maybe help my thinking.
I found PK/BG F919 at both the seat connectors; XY410A Pin 4, and XY420A Pin 23. It seems to have just one feed--at XY330A under the center console. I had to splice it to feed both the seat connectors, above, when I installe the Front Seats. I plan to spice it again to get to the rear seat connectors, XY430A and XY435A. I have discovered that it feeds all 8 Seat Vent Motors. All at Pin 1. My concern is that it's 0.75 wire all the way through the system. So, one 0.75 wire feeding 4 branches. I'm hoping it's just a signal. All 8 Vent Motors have 3 wires. This F919 0.75, a 0.75 Ground, and a unique 0.35 Vent Motor Control.