Spark plugs

Rocket 3 GT has anyone upgraded from NGK 4313 stock number to iridium 91909 types

Iridium plugs are over rated, imo. The only thing that they do better than std plugs is last longer. They are great if you never want to change spark plugs and end up with seized plugs, but apart from that there is no real noticeable improvement. For the exorbitant cost you will not get outstanding increases in performance.
Standard plugs work and work well. They are a consumable item that don't have to be replaced that often, but are cheap enough that when needed it's never an issue.

Thanks for tour opinion, but I would state that after a long strip down to get to the air filter and plugs, the additional costs are far outweighed If they last longer. My bike has only 7000 miles on it and the air filter is quite dirty and plugs are in.my opinion ready to be changed.

just an opinion ... air filter is going to be cleaned/replaced a lot more than the interval of those expensive new plugs, so you will have to do the strip down in any case for the filter ... just some thoughts