I've recently had some weird issue with my o2s. I installed LTs and a full exhaust 10k miles ago. Deleted rear o2s and got a tune. Everything was fine till a few days ago. It threw both p0153 and p0133 for both front o2s. I changed both sensors and cleared the codes. A few days later both codes came back. Why would it be doing this all of a sudden? Any thoughts?