I asked much the same question last month and, considering the replies I received, agree with HD-DOC (I think I do anyway).
Indeed your plugs show lean. Unfortunately that's normal with stock ECM settings but your plugs sure do look lean. My old (very old) drag-racing days memories say there should be a slightly brown/tan ring around the insulator and roughly 1/3 of the way down the "throat" of the plug.
Like Doc, I doubt things will get any better until you go the "tuner" route and, unless you want to rev to the actual red-line for the '96, don't do what I did and pay for the HD "Stage 1" flash. I like the extra revs. Your call on what the revs are worth to you.
Mine already runs almost as lean as yours but I still have the damn CAT. I also have an SEAC but you don't mention your air cleaner (another restrictive gizmo). If you do have (or go to) an SEAC or equivalent, then I (based upon good input from others) also recommend a tuner but would add "ASAP" to Doc's recommendation.
BTW: A positive indicator for destructive lean conditions or major pre-ignition is black freckles on the porcelain inside the plug. That's melted aluminum. Unfortunately, by the time that shows up you already have engine damage.
