Fouling #8 plug?????

Run a code scanner and see if you get any error codes.

In addition, a couple things I would check if it were me:

Pull distributor cap and check terminal inside cap for that plug wire for damage (unlikely, but a quick and easy check)

Test resistance of that plug wire ensure that it is not excessive (ie compare to resistance reading on another plug wire of approximately the same length).

Arc that plug wire's spark plug boot to ground, ie. a bolt/nut, and make sure there is spark.

If spark checks out, I would suspect a problem with that cylinder's injector, or with the rings on that cylinder's piston, but I'm not sure how likely either would be if you don't smell oil or fuel on the plug.