guide is available
here .
1. Get codes, determine the one that is failing. Replace only that one.
2. Use OEM Bosch part, not Porsche part. For part numbers, see guide.
3. Either do it yourself or have local muffler shop replace for about a half hour labor.
I did 1, 2 and 3b (because I was moving and in a hurry) and am happy and richer several thousand miles later.