BIG problems in cylinder #7.  We think we found the cause of the miss. The engine was actually running quite well even with bits of the plug missing. The remnants of the shattered ceramic insulator from the spark plug found a new home in the soft aluminum head and piston.
			Did I set the base timing too high? Was the octane rating of the gasoline inadequate? Did the boost go ballistic? Was the engine too hot? Was the plug damaged before or during installation? You tell me.
	After 40+ years of playing with engines, I have never seen a spark plug lose the upper 1/4" of insulator.
		I was very lucky this time, the cylinder walls and piston rings show no evidence of damage. The engine currently runs great.