We found that the factory length O2 sensors have a plug right in the hot area downstream from headers. I experienced melted wires and a check engine light that was hard to clear to pass inspection.
We use factory O2 sensors and extend the harnesses and route them over the inner frame rail away from all the header heat. This allowed use to run a really nice high temp wire shielding. It requires cutting your factory harness, but my car with less than 2,000 miles had compromised wiring from heat, so it was a no brainer to remove the damage.