Well, the service manual lists only three values on timing;
10 degrees @ 900 rpm @ no vacuum value listed
16 degrees @ 2000 rpm @ 0 vacuum (high load)
30 degrees @ 2400 rpm @ 300 mbar vacuum (no/light load)
These values are insufficient to draw a curve. What I could do though is put the digital timing light on our 89 Veloce, get a number of data points, and draw a curve(s). I try to get to it in the next few days.