[CraigG.]

Rotor Phasing Conflicts: This is the most frequent cause for a miss when using a Starter Saver or retard module.
The Issue: The Starter Saver retards timing (typically 10°–20°) only during cranking. If the rotor tip is at the end of the distributor terminal at base timing, retarding it further can move it completely past the terminal, causing the spark to jump to the wrong terminal or not fire at all (a "miss").
The Fix: Use a phased rotor or modify a distributor cap to verify the rotor's position with a timing light while the retard is active.
Voltage Drop Interference: The MSD 6A box is sensitive to voltage drops, especially during cranking when the Starter Saver is active.
If the small red (switched 12V) wire drops below 10V while the starter is engaged, the box may fire intermittently, causing a perceived miss or no-start.