My thoughts on these coils [ and connectors] is they are prone to a high fail rate due to extreme engine heat b/c they sit right on top of the engine and then they throw an engine cover over the top. This is definately heat fatique situation and one will notice that these coils are NOT oil cooled..like the old car were..and those old coils , being liquid cooled and remotely located from the engine where they had airflow would last a lifetime..so, not surprizing that a coil that has little cooling AND has to fire 2 plugs in a high compression engine does not have a life time that one would expect from a remote/cooled coil..
One will also notice that the plug connectors that always give the trouble are only the 3 under the coils ..they other 3 are not a as heat trapped b/c they are in the open air and not under a HOT coil..[ that is why we always
point to the 3 connectors under the coils as a first possible on 104 Waste Spark systems

Plus the fact that the originals were weak to begin with [ the blue stickered ones]
This problem can be diagnosed in 5 min with a scope, but for the diyer, persistance and parts swapping, along with some code observations and analytical thinking will get to the bottom of it..

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A Dalton