Spark Plug or what? Please Help!!!!!!

I have been having a problem with my 1997 aurora. The service engin light comes on. It starts blinking and the more i drive it stop blinking. My car is riding rought to when the light is on. However after a few days it goes out. I have had new spark plugs and wires put in. I have been to all the autozones in my city all most. Every time i go it a new code that they detect. (0307, 0306, 0302,) I have changed the coil packs on plug 2,6,7 still the same thing. I have removed the wires and seated them back. Still same thing. Can someone please help me?????????

do this... get a rubber hose that will fit in the coil pack and the end of the spark plug wire (vaccum hose) 1/4'.... cut 8 1 inch pieces,,,, stick them on the coil pack top and the other end on the spark plug wires,,,,,.... now get a test light or some aligator clips.... get a good ground on the vehicle.... make sure that when your doing this that you DONT TOUCH ANY METAL ON THE ALIGATOR OR TEST LIGHT LEADS..... ground the leads,,,,, now take one end of the lead and put it on the side of the hose in the middle (the spark plug wire will be on top and the coil will be on the bottom ( car running) when this is done.... it will take away any power going to the wires and no spark.... if the engine shakes while this is done then its ok... but if you do this and nothing happens.... you might have a problem with the plug, wires or the coil pack..... let me know how it goes... any questions my e-mail is [email protected]

Thank you all who replyed. I'm glad to tell you that the problem is fixed. It was the fuel injectors. I had what called a motor vac and it cleaned the injectors as well as all the major parts of the motor. It's runs and sound like new again. Only cost me 100.00 bucks. I'm very happy right now.