The 928S4, 928GT and 928GTS models use a Bosch EZK for ignition and a Bosch LH ecu for fuel injection.

The table below lists the different versions that exist and the Eprom software you find inside.

 
    PORSCHE BOSCH BOSCH   PORSCHE BOSCH BOSCH DIAG Feature
  Year Porsche LH number Bosch number Eprom number   Porsche EZK number Bosch number Eprom number  
Early 928s4 -87 unknown unknown     unknown 0.227.355.480   non DIA
928S4 1987 928.618.123.10  0.280.002.504 2.287.355.832   928.618.124.10 0.227.400.035 2.227.355.480 non DIA
1988 928.618.123.11 0.280.002.504 2.287.355.447   928.618.124.11/2/14 0.227.400.035 2.227.355.520 DIA, LH eprom 0.287.355.352 also exists
  1989 928.618.123.13 0.280.002.507 2.287.356.487   928.618.124.15 0.227.400.154 2.227.355.544 DIA
  1990 928.618.123.13 0.280.002.507 2.287.356.487   928.618.124.15 0.227.400.154 2.227.355.544 DIA
  1991 928.618.123.25 0.280.002.508 2.287.356.877   928.618.124.15 0.227.400.154 2.227.355.544 DIA, EZK eprom 2.227.355.334 ?? unsure

 

   

   
928GT 1989 928.618.123.14 0.280.002.506 2.287.356 486   928.618.124.22 0.227.400.164 2 227 355 584 DIA
  1990 928.618.123.14 0.280.002.506 2.287.356 486   928.618.124.22 0.227.400.164 2 227 355 584 DIA
  1991 928.618.123.26 0.280.002.509 2.287.356.878   928.618.124.22 0.227.400.164 2 227 355 584 DIA
                   
928 CS/SE 1988 928.618.123.12 0.280.002.506 ?   928.618.124.13 0.227.400.043 ? DIA
1989 928.618.123.14 0.280.002.506 ?   928.618.124.16 0.227.400.043 ? DIA
   

   

   
928 GTS 1992 928.618.123.30 0.280.002.514 2.287.357.477   928.618.124.30 0.227.400.197 2.227.355.341 DIA
  1993 928.618.123.30 0.280.002.514 2.287.357.477   928.618.124.30 0.227.400.197 2.227.355.341 DIA
  1994 928.618.123.30 0.280.002.514 2.287.357.477   928.618.124.30 0.227.400.197 2.227.355.341 DIA
  Data gathered from internet and research by Theo Jenniskens