I purchased a 2005 RC recently and just noticed it does not have rear O2 sensors. The pipes appear to be 3 inch with high flow CATS and Magnaflow mufflers. One of the CATS is chattering, so when I inspected it I noticed no rear O2 sensors. Will this be a problem in the future when I replace the whole exhaust system? How do I re-install rear O2 sensors when it appears the wiring is gone? The truck runs great, but is very loud and backfires at decelaration. Thanks for any info.