TWC System Low Efficiency Bank 1 code
#2
Drifting
I believe this code is referring to the catalytic converter on the drivers side of the exhaust. Is the code set and staying or is it a code stored in the PCM history?
#4
Drifting
Try clearing the codes and see if it comes back. It could be because of the Oxygen sensor after the cat too; do you have simulators or are you running the stock exhaust with the exception of the high flow cats?