My 1994 C4 LT1 sometimes just won't start after it's been running, Operating temp 200-220 degrees. sometimes it's just died driving down the road. But I leave it just sit for a bit, hour maybe a few it starts right up. By the way when it starts, it STARTS RIGHT UP!!! I  Don't have to turn it over, and over to get it to fire up!! I have done all the basic stuff to try to find the problem. I have fuel at the fuel rail. but I don't have spark at the spark plug?  Have replaced the optispark,ignition control module, and have bypassed the Vat's also. Did that first... LOL Now someone sad that it the battery votes was below 12.4 that could cause the car to start and run, But that the ECM would read the low voltage and turn off the car??? What... Someone also said that it could b e the temp control module? Telling the ECM that the car was over heating and do the same? Others have told me that the ECM is bad and replace it. I don't think so?? 

Fuel pressure must be checked with a gauge. if you are 1 PSI below speck it wont run. If in fact you must replace the fuel pump only use AC Delco or Denso. There are NO other pumps that will work at all and if they do it won't be for long.

You've listed just about everything that would cause this problem as being replaced. What you have NOT listed is any codes that are being set. Has it been scanned, or codes pulled at any point?
Operating voltage would have to get below 10v before the PCM would even consider a shut down.

Frist of all I want to thank the replies that answered my post and had a lot good idea's. BUt By chance I thought why not replace the coil along with a new set of plugs and wires.  First I did the coil because I knew that doing the plugs and wires would take hours.. LOL And guess what the coil was the trouble. It was the original one and I guess it just decided to go down fighting and not just go bad all at once like most do. Am still going to change the plugs and wires just not looking forward to that much... LOL Have drove the car to 3 car shows so far and a short trip about 275 miles. Starting and stopping and number of times over 3 days. She started right up every time,and didn't die on me once. So I pass this along to anyone that may have this happen to them. Don't overlook the small things... LOL 

|UPDATED|3/1/2016 6:58:36 AM (AZT)|/UPDATED|

I Don't have an answer to your issue but I do have a question; How did you bypass the VATS? I have 94 that I would like to bypass the VATS on also. Thanks

Your original post stated you had replaced the Optispark...I assumed you replaced the complete system....