Alan, you may be burning fuel in your headers, which would cause your headers to be much hotter than normally expected. Very late (retarded) ignition timing and/or very advanced cam timing can cause this. I doubt it is cam timing since such extreme timing would probably cause the piston and valves to collide. Burning fuel in headers can go from bad to worse if fuel tuning is based upon EGTs - the high temps would normally indicate a lean condition, so the EGT based tuning would result in the addition of more fuel, which will make the problem more acute.
If fuel is burning in your headers, you will likely experience other problems (shutting off unexpectedly) as you indicate. Did the paint on your headers burn more than you would expect?