Hy everyone, I'm new with subbies so please help me. I have a n 02 wrx with 142k on it. It is a manual an all stock besides an aem CAI. I pulled the codes with my code reader and it came up with P0171 and code P0420. I'm assuming some of you know what these codes mean( lean mixture on bank 1, and catalytic converter below threshold.) do these codes go together? Do you think both the 02 sensors are bad? Where should I start? All the plumbing on the CIA is tight. Please help, thanks!