I have a 93 Z M6 with 107,000 miles. So, I have run into most problems that can be encountered. It sounds like the opti crap is going out. I am on my third one. I will give you one piece of advise that will save you money in the long run. When I rebuilt the car three years ago, I replaced the opti spark, water pump, coil, ignition module and most of the other sensors to ensure trouble free operation as well as add CAI, headers, hi flow cat and exhaust. Well, 18 months later the new GM water pump goes out and ruins the opti. There goes about $700.00. Well, I took it to the local Chevy dealer and let them replace the water pump, opti and the alternator (bearing starting to squeal). When they replace the stuff now, they give a lifetime warranty on the parts and labor. Thank god I did it, 45 days later the alternator went out with less than 2,000 miles on it. Replaced for free. Just my 2 cents.
You will definately hear the fuel pump pressurize when you turn the key.