"Of note also is that the ECU operates at 5v whilst the coil operates at 12v."

I don't think those voltages are particularly relevant to your problem. The 12V to the coil is a constant, at terminal 15. The 5v EZK voltage primarily functions at the electronic ("logic") level, although it does affect the Power Stage. What the Power Stage does (under EZK control) is put a solid ground on Coil #1, to allow current build-up in the coil primary winding—then OPEN that ground, so the primary coil field collapses and iinduces a High voltage in the secondary for the spark.

I don't mean to dispute your approach, but merely to offer the possible benefit of nearly daily scanning of Ignition and FI problems here since June 2003, with no recall of any being solved at the EZK CU voltage level.
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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.