Tuning For Detonation

RustyRatRod said
It was 40 at 3000 RPM with 15 initial. Now it's 35 at 3000 RPM with 20 initial. Yes, I am running a vacuum advance.

OK you are currently all in at a total of 35* mechanical advance, that should work.
Have you considered that the VA may be adding more timing than the engine likes?
Do you know how much advance the VA is adding? Is your VA adjustable?