Have you checked the opti wire harnes and it's connectors. It runs between opti and passenger side of intake. Wiggle the harness while car is running to see if car quits. Also check connectors and pins.
Electrical part of ignition switch, located under the dash attached to steering column can cause these problems also.
Check coil and icm connectors and wires. Did you put heat sink compound on back of icm and it's heat sink when you replaced it? If you didn't, icm will burn up in short order.
Go to sticky threads of this section and open the diagnosing the opti thread. Watch the video and run the tests. www.shbox.com
also has opti testing, as well as, coil testing proceedures.
has most all 93 wiring diagrams you can view or download. PM me with your e-mail address and I send you the pdf files of ecm pinouts and ecm wiring chart to help you.
Have you checked for codes as not all codes light the ses. DTC's 16, 41, & 42 are all ignition codes that will stop your car from running, when active, but don't light the ses. Your 93 is unique in the lt1 family because you can read the codes by shorting the dlc terminals together with a paperclip. Short terminal A to B.
Lastly, I would put your car on a obd1 scanner that does running sensor data scans. Amazon sells the Actron CP9145 obd1 & obd2 scanner for around $140, a good investment as it will read your car and newer obd2 cars also. However you will need the CP9127 GM 12 pin dlc adapter also for $35