Pontiac Problems? Ask a Mechanic for Answers ASAP
Did these repairs address any of the codes you have?
None of these codes should result in limp mode, were there other codes?
After you did your repairs, and cleared the codes. Then drove it 5 times, what codes returned?
If I disregard the codes and respond based on the information and symptoms. The flashing check engine light is for a misfire. The max speed of 20mph makes this look like a transmission issue, or a restricted catalytic converter. Do you own a vacuum gauge to check the vacuum at idle operating temp? Have you checked the fuel pressure? If you remove the line from the EVAP and block the line, does that help with the EVAP ruled out? Can you run a compression test to verify all cylinders are contributing equal? Can you test the injectors and coils to verify they are getting power and command from the computer to pulse?
Converter issues associated with restriction does not result in O2 codes.
Yes removing the upstream O2 sensors for a short test drive is okay to do to rule out the converters.
You would remove the vacuum line from the EVAP vent valve that dumps fuel tank vapors into the intake.
On the oil gauge you would need to hook up a pressure gauge to test the oil pressure to see if the gauge or sending unit is to blame.