[GM Line Rat]

It sounds like a poor fuel delivery Problem.....Has the fuel pump ever been changed in this car or the fuel tank inspected for rust or a dirty fuel pump pickup screen?

Here the other suggestions under the symptom "Engine hesitates under
Acceleration" (I left out items you have allready addresed).

1. Inspect Fuel System Pressure..... Incorrect fuel pressure being delivered to fuel injection system. (Use a fuel pressure gauge, connected to the Schrader test Valve at the back of the fuel rail, test for proper fuel pressure).

2. Inspect Fuel Pump... Improperly functioning fuel pump or circuits.

3. Inspect Throttle Position Sensor - Faulty throttle position sensor or throttle position sensor circuit.

4. Inspect Fuel Tank - Contaminated fuel from rusted or deteriorated fuel tank. (If the has been ran with several tanks of gas, this would not be a issue).

5. Inspect Accelerator Pump Diaphragm - Damaged or faulty fuel injection accelerator pump diaphragm.

6. Inspect Mass Air Flow Sensor - Improperly connected or faulty mass air flow sensor. (What method did you use to clean the MAF?)

7. Inspect Oxygen Sensor - Damaged or faulty oxygen sensor or circuit. (This should have set code 13 If O2 Sensor was bad, Has it ever been changed? Recommended to change every 50K Miles).....Use AC-Delco OR Sensors only!!!

8. Inspect Fuel Injectors - Plugged, dirty or poorly connected fuel injector(s).