difference betwin ECU numbers ???

Hello
Im looking for information about Engine ECUs numbers and difference betwin them.

I have in my GEMS 4,6
6645 - but when I swap it for another one with same numbers, my engine run very badly.
I find on e-something, many of ECUs to 4.6 and some of them have different numbers ,so what is the difference ?

5740 - ?

:emps1:

is that mean you have no idea .. right

I imagine that at least you would have to clear the trims with diagnostics.