v8a6, thanks for the valuable info in your posts (and everyone else for that matter). As someone who (perhaps foolishly) plans to keep a 2011 S6 for a long time, I’ve bookmarked this post. Thankfully, I have done most of the things suggested but have not gotten into O2 or cat changes yet.
Question about JHM tunes, since I have already done JHM TCU and ECU tunes, would either need to be done again after the O2 / Cat changes? Sorry if there is and obvious answer but I’m only smart enough to be dangerous.