[Mrmerlin]

you will also have to modify the light housing indentations on the chassis to fit the protrusions on the later S4 bumper,
otherwise the rear of the PU cover will not fully insert to position ,

its a bit of work to make this modification,

Next question is why would you do this to begin with?
the early rear bumpers have a coolness about them the later S4 series has lost IMHO