nighttimedaydreamer

Hello all, I have a 2003 Cavalier Ls with the Ecotec F Vin motor, 4 door, 180,000 miles, I am the second owner. So I was driving one day and when I stopped at a red light the motor started idling rough and then immediately died. I cranked and was able to get home without any other issues. Driving it the next day I noticed it fluttered (idled rough when stopped) except when I was driving, as long as I am moving I am fine, but it will die every once in a while when stopped. I replaced the spark plugs, ignition coil pack and control module, air intake sensor, map sensor, throttle position sensor, and idle air control valve. The car ran great for a week, I drove it about 450-550 miles during this time, but periodically it would have a much fainter rough idle and it did die on me once when I was parked without any leading indicator that it was going to die. Before I replaced the parts, I cranked it one time and it revved high and gave the P0300 code, so I changed out the parts and this went away, I did a battery reset. I was driving home today and when I went from park to drive, the motor revved high and then gave the P0300 code, when it did this the cabin filled with the aroma of gas and this has never happened or I may have never noticed. I stopped the car, went, and checked the connections on the parts I had replaced thinking maybe I missed a clip, but everything was connected. I cranked it and the code was gone, it drove great all the 1/2 mile home, even when stopped. Has anyone dealt with this before, any suggestions? I am wondering if this could be a blocked purge valve canister or timing chain-related. The thing that I do not understand is why it gave the code when I went from park to drive?