1995 M3 Chip Upgrade (post 95 Build Date)

[DSM]

I have 1995 m3 automatic with build date 8/95. It seems that finding a chip upgrade is tough. Can anyone tell me why the pre 95 & post 95 computers are different? Can anyone tell me where to get a chip? Will the pre 95 computer work in my car?
Thanks

[Fergy]

pre 95 computer will work but You must check wiring diagram to be shure about wiring (they can have a few wires more or less).
new computer have few upgrades (one is more power to engine-different parameters).