when you get knock you need to increase your octane fellas. what you're saying regarding using 93 being unecessary is usually true, but i would highly doubt his knock will go away with using a fuel that tends to have a faster/less controllable burn. normally on an ls i would recommend using 87 or 89, but 93 has less resistance to knock. if you're knocking you're either too lean or too far advanced or way retarded with timing.

i would ditch the iridium plugs and go with standard ngk or ngk v-power. if you still knock on the stock recommended plug then go a heat range colder.