If it helps with a possible diagnosis path, it's actually the opposite. I may have typoed or something.

It runs fine after the CEL light is on. Initial driving is often sluggish and unresponsive with the car struggling to maintain speed or accelerate unless floored. Once the light trips on the change is immediate. You would never know there is an issue other than the light being on, because after that time the car never even hiccups. It's followed this pattern for quite some time now. It goes through the same pattern after every shut down and recrank, hot or cold. Rough driving until the light comes back on, then immediate normal driving conditions.

 

Code 43 is most likely a problem with the oxygen sensor circuit.

If the Check Engine Light is on, with code 43 and there is poor drivability, then it may be due to a fuel supply issue. You are not experiencing poor drivability when the light comes on.

It may just be a lazy O2 sensor.

Edit: I just re-read the long thread; you've replaced it twice. Still may be something with the O2 sensor circuit (e.g, sensor or wiring), or even ECU.

http://www.justanswer.com/uploads/ho...rd_code_43.pdf