Old Audis use Hitachi ECUs to control ignition boost etc. functions. Below is pinout of MAC-11, used at least with MC1 engine.

1. Cold Start Valve
2. Ignition Module Ground
3. no connection
4. Hall Sender return ground
5. ground
6. ground
7. Tachometer
8. CIS Freq Valve
9. Ground
10. Coolant Sensor
11. RPM Sensor signal
12. TDC signal +
13. TDC signal -
14. no connection
15. Knock Sensor Positive
16. Knock Sensor ground/shield
17. Boost Gauge
18. Ground
19. Waste Gate solenoid control
20. Idle Switch
21. Fuel Pump relay ground control
22. Ignition Module control signal
23. Intake Air Temp sensor ground return
24. Intake Air Temp Sensor +
25. Hall Effect +12V supply
26. Full Throttle Switch
27. Hall Sensor signal
28. RPM/TDC shield wire
29. RPM return ground
30. O2 Sensor shield ground
31. Fault code light control
32. Brake Light Switch
33. O2 sensor output
34. no connection
35. +12 Voltage from ignition switch

For MSAVR most of stock wiring can be reused, but some extra wiring is required though.

See InputTrigger/AudiTrigger about RPM/TDC signal timings.

More information about installing MSAVR will follow once there is some more progress with project.