HEI module going spastic?

..............are you ABSOLUTELY certain that the pickup coil is wired with the correct polarity?

Check all 8 plug wires AND the coil wire for continuity. Remove them, hook your ohmeter up using a clip lead on at least one end (if the ohmeter leads contact a finger on both hands, it will give your body resistance)

With an end of the wire in each hand, shake the wire looking for resistance change. This is best done with an old analog meter, or with a digital that has a bar graph on the display.