Three weeks ago, I have taken my 2000 Toyota Corolla to replace a Catalytic Converter; as well as the Oxygen Sensor. Where I paid $448 to replace it. Therefore, the Check Engine light came on and I took it back to the mechanic where I gotten the vehicle worked on. The mechanic replaced the faulty oxygen sensor. Now the vehicle seems it wants to hesitate and it gets sluggish when I pull from the stoplight/stop sign; as if the vehicle wants to stop altogether. I taken the vehicle to Auto Zone to do a code check on the vehicle. And it read as the following: -Faulty Heated Oxygen Sensor (circuit slow response) -Open or short ciruit condition -Poor electrical connection -EFI relay fault It has gotten to a point that I left the vehicle in front of the house and started taking public transportation; because I don't want the vehicle to break down on the street or on the expressway. Since I returned to the workforce two months ago, I don't have the financial resources to purchase another vehicle. I am at wits end. Any suggestions?