found some info only:
"S" position (for sport mode) or "P" position (programmed).
Standard EDC III has S and K
http://www.kindel.com/bmw/how_to_identify.htm
I found a comment on the German M5 forum, that the EDC III plus was only available on M5 3.8 with Nurburgring package, the normal M5 just had EDC III.
Looks like the previous owner installed in the E32 Alpina B 12 the wrong control module from an M5 in Nurburgring specification.
Will try a normal EDC III control module I still have on stock.