On '99-and-newer Mustangs, Ford moved the rear brake line and added an additional exhaust hanger to each side. Both of these interfere with the sway bar chassis mounts and changes need to be made. There are two hangers-one for the tailpipe and one for the muffler. The tailpipe hanger will be eliminated. Altering the hangers won't cause any problems because you will revert to the '79-'98 hanger configuration, where there was only a single muffler hanger. We began our alteration by cutting the hanger that goes from the tailpipe to the rubber mount.