Car idle rough p0300

What is your question?

Had plugs and wires replaces 5 days later coming to a stop engine light starts flashing and car started jerking and shaking bad. Had mechanic check and was told was ignition coil #2 wasnt sparking. We went to junk yard and got one hooked it up and still did the same thing but coils and wires were sparking. We took 2 front spark plugs and they were already black it got dark so he hasnt checked back 3. Any suggestions i just purchased this car for $5000 and dont have any extra cash. Water pump believed to have water pump leak

What makes this problem better or worse?

In park if i give it gas it goes away until i let off

How long has your 2007 Chevrolet Impala had this problem?

2 days