Most likely the Optispark is bad and water pump probably leaking on it just a little
+1. This can also cause intermittent backfiring and won't throw a code. If it is this, make sure you update your optispark to the one with vacuum. I can't remember if 94 is when they started that or not. My 93 didn't have it.
'69 SS396 X66 L34 08D (8/22/1969) M21 BS
460ci Gen VI 9.75:1
241/249 @ .050" .625/.625 110 LSA
"The galleries are full of critics. They play no ball, they fight no fights. They make no mistakes because they attempt nothing."