You will see an improvement over bad plugs (like has been stated), but there will be no performance increase over new-ish stock plugs. Hell, even plain copper ones (which won't last very long).
The Denso Iridium's don't have double sided plating, which is needed for the rear bank (because they fire backwards).
A spark is a spark. If it starts a flame kernal, it's done it's job.
