Hey, John, that sounds exactly what happened to me. After a whole bunch of miss diagnosis, it turned out to be the opti-spark . many guys told me that and it was true. There is a module inside the opitspark that fails. If if was like mine and origonal, there is no way to change the module without changing the whole distributor. ( you can change some of them with the aftermarket distributors ) If you can email me direct I will show you the pictures of the inside of my opti-spark, it was rusted so bad it is hard to believe the car ran at all. IF by chance it isn't the Opti-spark I do have abrand new ECM for the '93 LT1 I want to sell. Thney thought it was the ECM , so i bought one , only to find it wasn't. So I have ane ECM that is really of no need to me.
I would see if someone has a good Sun Scope and see if it is the Opti-spark,. The guy that diagnosed mine , showed me a print out of it whejn cold and running fine, and then when she got hot and then died. It is eaxctly like a heart monitor, and shows the heart beat and then , it is like the car is having a heart attack, the Opti-saprk can't figure out which cylinder to fire...email me.. Jeff