Chevrolet Repair: 1989 chevy pick-up misfire., spark plug wires, chevy 3500

Question
I have 1989 Chevy 3500 pickup w/ 454 EFI.
Changed plugs, rotor, cap, new oxygen sensor and fuel filter.  After doing so I have a bad misfire. The truck runs terrible. It seems to be from the #1 cylinder. I put a timeing light on it and the light would flash intermittingly when it would fire. Pulled the plug and that is what it looked like. Not always firing. The other plugs looked ok. When I changed plugs all the old plugs looked good. Checked plug wires and firing order. The only code that was flashed was a 24 TPS which it needed and I replaced.
If you have any possible solution to what Is going on or what I did wrong please help.
     sincerely Dean.

Answer
Plug wires are made of CARBON PILE and not wire anymore and this carbon pile tends to break down over the years.

here's a little trick for you to try:

After it gets dark, start the engine and let it get to normal operatring temp and using a spray window bottle like a windex bottle set on MIST, Fill the spray bottle with water and start spraying all your spark plug wires and see if you see any arching of spark from the wire(s).