Today I pulled the cap and rotor and this is what they look like(photos attached). I cleaned the contacts lightly with 1000 grit sand paper and throttle body cleaner.
I just took another close look at your photos, and something caught my eye that
is either a cosmetic manufacturing flaw, or it's the start of the way these crab caps
blow through from the center terminal to the #3 cylinder spark path that runs
adjacent to it.
To get a better idea of what to look for when these caps burn all the way through,
check out this photo that
@L31MaxExpress shared over
HERE.
After viewing that photo and appreciating the crab cap failure mode, please take a
gander at the marked up versions of your photos that I attached. If the cap is
burning through, it's juuuust starting.
UMP Cap and rotor, spark plugs, ngk wires will be here on Thursday.
The UMP Cap & rotor is good news, looks like it will arrive none too soon.
And finally I was thinking about the 'many miles & many moons' comment
I made earlier. One of the things that shortens the life of a lot of spark
plug wires is all the tugging/twisting/yanking when the spark plug wire boots
weld themselves to the spark plug porcelain, especially after all that radiant
heat from the exhaust manifolds is layered on.
Once I finally started using dielectric grease without fail with every plug change,
I stopped suffering the frustration from all the above. Now the spark plug wires
always came off like factory fresh, and this was in addition to keeping misfire-
inducing moisture out of the boots.
If you follow the tips in the 3rd attachment, this will put the finishing touches on
your mid-life refresh of the ignition system. Wish the Vortec setup wasn't quite
so fussy/demanding, but in the interest of meeting the needs of added power +
tightening emissions starting in '96, the design engineers really pushed the ignition
system for max performance.
And now that we the consumers provide the final QA function for so many companies,
it's really become a chess game to keep these dizzy systems working in a brave new
world where normally every cylinder gets it's own dedicated stationary coil feeding it.
Hope this helps. Best of luck --