engine is missing at idle, changed plugs,wires
I’d replace the distributor cap and rotor too, and check for vacuum leaks.
Generic cap is $100. GM cap is $400. 8 coils?
Hmm, LT-1 is the victim of an OptiSpark that is anything but Opti!
You might want to read this.
http://www.lt1howto.com/articles/optisparkfaq.htm
This things are problems, pure and simple. This site can direct you to solutions. Swap for the factory cap and rotor or an MSD unit for about $400 to $500.
Given that the belts, water pump, crankshaft pulley, and a few other items need to be removed to service the cap and rotor, I highly recommend you use only quality factory parts. I’ve seen too many problems with the aftermarket units.
The link by @Mustangman is very informative. If I had this problem and was willing to do a little experimenting first before starting on replacing the opti-spark stuff (which might prove expensive), I’d be inclined to see if a simple cleaning and drying out of the gadgets might work. Remove as much of the opti-spark stuff as you can and let it sit in a dry spot outside in the sun for a couple days, meanwhile clean any oils and/or moisture out of the housing where it resides in the engine compartment. For moisture in the housing, I’d also use one of those things that comes in the box w/cameras, that moisture absorbing pellet thing. Heat it in the oven at a low temp for a few minutes first to drive away any moisture it is retaining. Then put it in the enclosure, seal it up, and let it soak up any remaining moisture in there.
A dropping cylinder is also a possibility along with a dozenish other things. It’s a 93 with ? miles on it so compression is certainly something for consideration.