sounds like an opti problem. 93 and 94s theres more to the opti than the newer ones. cam sensor is in there and a few more things with cercuits. on the 93 the map sometimes will do what you are talking about but you have a maf and i dont know if there simular. try umpluging the maf when its acting up it should revert to default. heres some words from yoda pete on optis:

Just for the record, the LT1 engine management system is a bit different than that used in most other engines. The clocking sensors (CPS, KPS, etc) in the LT1 engines are incorporated the optispark distributor and are not individually replaceable items, so a fouled up opti will prevent the engine from running. On OBDII engines (1996 & up) an individual crank position sensor was added to detect misfires via variation in crankshaft velocity, this item required a different front cover. If this sensor goes bad, the engine should still run, but the MIL will be forced on. Also, the PCM runs the engine on open loop during start up and until the O2 sensors come up to the proper temp. O2 sensors are ignored. In open loop operation the PCM relies on predefined fuel and spark maps; however, it does look at the ECT, IAT, MAP, and TPS.
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Pete

another from pete:
The problem with the opti is that it performs many functions that usually are done by individual sensors. Changing just the cap and rotor usually does not accomplish much as the real problem is corrosion attacking the internal components.

 

Did you test your fuel pump relay with a jumper before you changed ICM?