At first glance it would seem that if you have the gearbox control ecu that would avoid any communication issues on the CAN bus . That would then require looking into whether the gearbox ecu can be made to work with your 5hp19 gearbox.
On the wiring diagrams , start with the main ecu [J220] multiplug as an example - then we can see injectors 5 to 8 are supplied with a current from fuse [ S116 ] 20A via a black & grey (yes , that is the correct way to spell it
wire common to all four. Then from injector 5 [ N83 ] for instance , it has a brown & white wire to ecu pin 97 . The part brown colour indicates an earth switching control. A solid brown will always be a ground wire.
All ground connections go the base of the diagram , as can be seen by coil [ N323 ] pin 2 of the multiplug and the location of the ground point.
Pin 3 of the coil multiplug has a white & brown wire going to ecu [J220] pin 103.
The cambelt interval for your engine is 80,000miles / 6 years , always recommended anyway.
no other items to worry about.
As someone who runs a 28 year old german car , as has so for the last 21years , it does not need constant maintenance and does not have constant mechanical / electrical problems.
