I just gutted mine a few days ago and have notice great improvement in gas milage and drivability. My mechanic told me that they took off the entire exhuast assembly (had to remove one of the rads. to do that) then cut open the cat housings and cleaned all that sh%& out. They then took it to a specialized welder to close it back up. Best thing that ever happen to my Contour. Good luck, John
