I finally found the problem with my own ignition rpm drop and rough running on one side, and you may find it helpful. All along I had thought it was ignition modules or carb sync.

Pulled the plug wires, tested each pair (top 1&2, bottom 1&2 etc) and found high resistance (greater than 15,000 ohms plus or minus 800) on one pair (top 3&4). Pulled the caps, found a bit of corrosion on the plug wire. Trimmed the wire 1/4" back to shiny copper, put a drop of electrical anti-corrosion spray on it, replaced the plug caps with new caps, tested the resistance (now in spec) and presto, the problem disappeared.

Sorry if this isn't quite on the thread track, but sometimes problems seem to be inter-related.