I told you how to eliminate the HAC as a suspect. The HAC is quite low on my list of suspects.
If the crack in the coil pack could either allow for an arc to ground OR allow moisture inside then yes, it could cause a stumble. If it's on the low voltage side it's unlikely to cause a significant problem but I suppose it's still possible. A picture might help. Filling in the crack with enamel may patch it long enough for you to go for a drive and see if that is the problem.
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