Thanks great inputs. I suppose I should not have drastic changes in the chart. When I watch the timing in real time it behaves smoothly. But I can certainly reduce the timing and hopefully kill any detonation and go from there.
What you are shown on the screen may be smoothed too depending on how the display filter works and what the update frequency is. If occasionally the values hedge to the low end of say 64kPa between 1200 and 1800, you might get a little blip of excessive advance for a few revs even if it isn't going to the full 32-33, it can likely be well above the 16-20 expected.