Car has rough idle and wont stay running

Put car on bubbys computer and keeps saying #3 cylinder missfire.It cut a plug wire in half.So I put new plugs and wires on it.will start but you got to keep it reved up at high rpm to keep it running as soom as you let off gas it stops running.Before all this happened when you started it it would be at low rpms like it didnt want to stay i would give it a push off the gas peddle once and it would run fine.

How about telling us what year GrandAm you have and how many miles. Auto or manual and any recent history of maintenance or other problems. How long has it been doing this? Did it happen suddenly or come on over time? How about maintenance? Have the air and fuel filters been replaced according to schedule?

From the symptoms, the air and fuel aren’t in the correct mix (ratio). Disconnect a small vacuum hose, and see how the engine runs.
Clean the MAF (Mass Air Flow) Sensor with MAF spray cleaner. Clean the intake tract, iacv (idle air control valve), and throttle plate and bore, with Throttle Body spray cleaner.
After (if) you do these simple things, let us know the results.