From what I can see in FAST for S1's the original ECU was P/N: 23740-0V300, then it changed to 23740-0V301, then to 23740-0V310,
and then there's an alternate number which is 2374M-0V310.
Doesn't explain much though, and you wouldn't think the wiring would change.
Ah well, will wait to see what differences there is.