Can you adjust timing while it's running at idle? Advance until it no longer makes the motor "happier" then back it up a little and test it in out of gear and at low speed high vacuum driving and see how it drives. Can you log the vacuum to get a feel for how much vacuum the motor has at different driving scenarios?Not sure I can adjust the scale, but doing the conversion it idles around 16 inHg. Really the chart is almost a direct kPa reading already, just in absolute pressure instead of gauge. To convert basically just invert the scale so the top is 0 and the bottom 100. That would put the idle at 45-50 kPa of vacuum.