93 LT-1 Forefiring @ 3000 rpm & above Problem

[glasswater]

I have a 1993 Mastercraft pro star 205 with the corvette LT-1 that is having ignition issues.
I have replaced everything including the long block and it has the same problem. The engine makes a popping noise "Forefires" into the intake manifold when the engine is at 3000 RPM and above.
The computer program from OBD diagnostics says the temperature is jumping from -49 to 290 degrees and the MAP sensor is not working? I have replaced the map sensor three times, the entire wiring harnes, and the temperature sensors four times. I have also replaced the 4 coils, the ECM, the knock sensors, the thottle positioning sensor, the Magnetic crank shaft positioning sensors, the fuel pump (twice) spark plugs & wires, 8 injectors, the list goes on & on... If anyone has ever know someone who had this happen to them please let me know.
Is it the MEFI 1 computer that is no longer available?

Jon 262-370-4005