I noticed in buick manual that came with car that if your regal has turbo 3.8 that the plug gap should be .045.I have always run .035.I kept the original plugs and checked them.....sure enough .045. ACR44TS
Since "94, I've always gone with a tight .030" on my street boost tunes. And tighter with race gas boost levels.
And Autolite # 23's down here in the south for iron heads. Autolite race plugs with aluminum heads.
YRMV.
I noticed in buick manual that came with car that if your regal has turbo 3.8 that the plug gap should be .045.I have always run .035.I kept the original plugs and checked them.....sure enough .045. ACR44TS