I'm running mine kind of standalone, as the mk1 has I'll need to check, but from memory
It'll flag missing abs, Dash, crash sensor.
I have pulled out all the sai second lambda and numerous other bits and it's not limping.
Some things that u might think are important are oil level and oil temp, speed, but the ecu doesn't read them
I'll find u a proper list when I'm not on my phone, but rubjonny on the mk1 golf forum is a real wiring expert and will answer most things.