Oxygen sensor

[Bohnseye]

Had long tube headers put on my 98 LS-1. Had an service engine light pop up. Its Sending out a Oxygen sensor week code. The tech said sensor was good and turned light off for me. Hasn't came back on yet....but ive only drove a few miles since. Does anyone know why its sending the code? Engine lights drive me crazy and don't want an issue of it popping on and off.

Thanks guys