My z28 will miss about 3 grand and about 4200. I have changed plugs twice. could it be the map sensor mat sensor or o2 sensor? when you give it gas it wonts to die and back fire in the intake what could be causing that?

 

Check engine light on?

 

have it scanned for trouble codes. could be a bad plug wire, have a look at the engine in a very dark place and see if u can see spark coming from the plug wires. worst case would be the opti.