George said:
1)   If you advance the timing,  the EGTS will drop.
    2)   If  hold the spark initiation timing event to a constant value,  and you
use a spark source that provides a more consistent and quicker formation of
the flame kernel,  the EGTs will drop slightly.
    3)       If you use a “standard” ignition source,  but advance the timing
slightly,  you get exactly the same combustion event with the same horsepower
and the same peak pressure and the same Theta-pp, as you get with item 2),
above.  
  It is fundamentally simple.  That is all there is to it. 

Really...

Have you ever had one mag drop 300 to 500 RPM during run up?  Then, run the engine at higher power and leaner, re-check the bad mag and have the drop be 50 RPM. Unless JC dropped in for a quick parts change that I could not detect, the ignition source did not change.  So...what caused this condition?  We all talk about "fuel rich", carbon and oil fouled plugs.  Why won't they fire?  Could it be there is not enough spark energy?  If this is so...would more spark energy help?  Try setting the spark plug gap at .080"....I'll bet the engine will start and run but maybe a little rough and maybe it won't even start and run after 50 hrs.  When the engine is running "rough"....is it misfiring?  Is it the same cylinder every time that misfires?  Why does an engine misfire at WOT and not at idle?  Why does an engine misfire through the plug wires when the engine is wet?  I'm not looking for answers...I have them. Would more spark energy change/help all of this?  I personally think a standard mag is a marginal choice for turbo charged or high compression 6 cylinder engines.  I do believe a standard mag will make them start and run, but I don't believe that is all there is to it. Oh...I also believe that all of these marginal conditions can affect EGT. I also believe that if all the ignition hardware is functioning satisfactorily, then "that is all there is to it". Finally, the auto industry has evolved for mags, to battery ignition, to HEI , to individual coils at each cylinder with very short secondary leads.