Interesting theory about the increased manifold pressure adding to this SAG problem. I recall Ed's thought on this from the past as well.
Since I use a turbo for mild boost (usually just for climb performance), I'm seeing increased pressures often, but never any SAG that I can remember. (it's been a few years since I last flew)
Dave & John both use turbos for far more sustained boost than I do. Have either reported SAG? And with what fuel?

Todd C-FSTB RV9 Turbo13B

The higher the cylinder pressure, the higher the voltage required to jump any gap. The slow rise time of a Kettering system allows for voltage to leak across debris on a dirty center electrode. Eventually enough voltage will follow the leak path and a misfire will occur.

 

To test for SAG while under way, just pull off some throttle. The cylinder pressure will be reduced, and the plug will start firing as normal. Returning to full throttle will return the misfire.

 

You can cure the problem by installing new plugs on a time basis. You can clean the plugs. You can shorten the gap on medium tip ice cold racing plugs.

 

Or, you can use a capacitor discharge ignition system on the leading, or both plugs. The plug gap is just a big variable resistor. Low cylinder pressure=low resistance. High cylinder pressure=high resistance.

 

Not only a disorder of rotary engines. Common in all internal combustion engines.

 

 

Lynn E. Hanover