104s are too cool for a N/A engine. AL605s are one heat range colder for the N/A engines. 104s are two heat ranges colder than stock. AL606 is the stock equivalent Autolite plug.

Plugs aren't the first place to go for knock. Tuning will help out immensely, though as I'm finding out it isn't always easy going.

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2004 Impala LS - got some mods
NAIOA Moderator

Making you think twice before picking on Impalas