Hello,
after more than 2 years of research and development and more than 1000€ of hardware costs i managed to understand how the immobilizer between engine control unit and skreem works.
And it was possible for me to find a way on which I want to replace the Skreem module. The first (and maybe most difficult) step is to unlock the immobilizer with my hardware and then start the car. This is done
The first prototype on a breadboard is finished and working.
See:

The next steps are to build a second prototype on a perfboard and install it in my Crossfire to do a long term test.
At the same time I still have to find solutions for the remaining functions of the Skreem module like opening and closing the car, deactivating the alarm system etc.
The goal of the project is to replace the existing Skreem module 1:1 with my "Skreemulator".

Greets Andre