Help, Please. 2006 Cadillac DTS
 

I have a 2006 Cadillac DTS. While at the gym I started my car. And it began idling rough, I gave it more gas and it started running a little better. I then cut off the car, and probably around 20 to 30 minutes later restarted the car. The emission light came on and would not go out. The next day I drove the car to Pep boys and they pulled the codes. The guy stated it was too much air in cyclinder 6. Told me to take it to dealers. But the light went out. Drove it twenty miles, trying to reset the computer. It ran fine. Drove it the next day car made a clunky sound when I would accelerate hard. Then the traction control light came on, and stability track started flashing. When I finally stopped and cut off the car, and restarted it the lights went out. Car drove fine. Until today when I started the engine and my emission light came back on. Then stability display followed by traction control light needs service. What could be the problem? They have replaced PCM computer, two years ago. I read on one of the threads about running the car while filling the car up with gas. I did that twice this winter. Could someone please give me some Advice. I am very worried about my automobile.