First, go get the code scanned or scan it yourself with the SCT and figure out what your car is telling you. Might be that it is completely different from an exhaust problem.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.