ORIGINAL: Klonger
...On an OMP 47 Edge profile using a 12.25 x 3.75 APC, 10% Byrons fuel, OS A3 plug.
Ken,
Get rid of that OS A3 glow plug!
It was never intended for your engine (even though the manual does list it a suitable{???}).
The [link=http://www.os-engines.co.jp/english/line_up/plug/pluindex.htm]OS Japan site[/link], where they're made lists this plug as suitable only for engines smaller than .32 (and the .40LA) and for break-in...
Because you have to run this engine richer, to preclude detonation from this hot plug, it will not run well in the mid-range.