Just my opinion but I would go in this order until the problem is solved:
1) Check old plugs for carbon tracking, particularly cylinders 2 and 4:
If you find it on a plug then replace the corresponding wire because it is toast. According to GM this is a particular problem on 93-93 L27 and L67 engines. I don't know why.
2) If you have a multimeter, check the resistance of the wires. Make sure they all conduct electricity.
3) Check the gap on your spark plugs just in case they were knocked in the shipping process.
4) Replace all the wires.
5) Check the resistance on the ignition coils.
6) Excessive alternator output? Now I'm running out of ideas.
My money says wires. I've had bad wires twice.