You mentioned what about no drop on magnetos, but didn't answer. Timing too far advanced is the thing to watch for. With electronic ignition it could be due to timing curve.
The water method of removing ethanol from mogas should never be used in an aircraft. You will have fuel with an unknown octane number. 85 to 87 typically. Look up CBOB gasoline
You mentioned what about no drop on magnetos, but didn't answer. Timing too far advanced is the thing to watch for. With electronic ignition it could be due to timing curve.
The water method of removing ethanol from mogas should never be used in an aircraft. You will have fuel with an unknown octane number. 85 to 87 typically. Look up CBOB gasoline