I have a 2003 Mustang GT and right now it has a rough idle and it is throwing codes for the upstream o2 sensors which I have replaced, but still has the codes. Background on the car is it has headers on it from when I purchased it, don’t know what kind, but they rusted out just behind the flange at the cats, so she’s running open headers in both sides. Though I don’t think that should cause a problem with how it runs. Any ideas?