On the RS Turbo the igntion is ECU controlled by the silver box, but the distributor still needs to be set-up so the base timing at idle is correct as even though the ECU controls the timing, if the base timing is out (retarded for example) the whole 'map' will be retarded, same goes for being over-advanced.

If you're setting it up, be careful you don't get any 'pinking' 'detonation'

Make yourself some 'det cans' and tune the car so no audible 'det'

Or even better get it set up by an expert on the dyno.

Also remembered the 12 degrees base timing should be with the vac hose from the ECU removed/blocked.