Observe closely, the white and the yellow wires from EI boxes and their connection to firing coils. A mix up can result in an engine that runs sort of ok, but not quite. Also, a big mag drop at higher power settings may also occur.
Example: Follow the white wire connection
Circuit "A" Fires

• 3 & 4 Bottom
• 1 & 2 Top
• The white wire from circuit A EI box plugs to the white wire on firing coil 4B/3B

On Circuit "B", the white wire from the EI box plugs to the white wire on firing coil 3T/4T