I always questioned the 4's from a logical standpoint.

An arc goes to the path of least resistance so it will always go to one of the four points. Yea, if the good point becomes foul it has 3 others to choose from. Problem one doesn't become foul on its own. Therefore, I never bought them.

Mine are 103s. Daily driver. Had Bosch iridiums before when I was N/A. No issues with either.