You have to modify the hangar closest to the front of the car (near the swaybar) and rotate the flange of the axle-back. Its easier to get the whole cat-back section and use that... though that may not bolt up perfectly to the cat section. Any exhaust shop should be able to do it for you.
I am thowing one of thse on my 01 RS very soon, everything look like it will line up, but I am going to goto a shop and have them make some 2.5" mandrel bends from the cat to the axle back. Should be less then $100.