I have a 1997 body with a 1995 LT-1 true Z-28 engine with 66k miles on it. Had to replace the original optispark due to seal leaking and getting water in it. After about a year out of nowhere it runs horrible after it warms up. I have read other threads and most seem to point to the optispark at this point. I have replaced spark plug wires,coil, ignition mod, temperature sensor in heads and in the water pump, new spark plugs etc.

 

Have you scanned it? "Warm" means its transitioned to closed loop. May be a problem with the O2 sensors, or possibly the fuel pump overheating.

 

FYI the temp sensor in the head only drives the temp gauge; the temp sensor in the waterpump is what the PCM uses to determine temp for initiating closed loop.