Update: Oddly I took the J shaped Vibrant O2 spacers off and used some straight spacers that were given to me with the test pipe. Since using them, no check engine light. No need to switch tunes, now.
With the new custom test pipes and catted down pipes, the O2 spacers I got just aren't cutting it. I got some different kind O2 spacers on order, but I fear I'm always going to have issues with the Check Engine Light (CEL). Sadly my current tune with EPL doesn't offer a "test pipe" tune. I really do love the burble and soft crackle you get with the new adjustable tune they just released. While they have been nothing but super helpful, I feel like my options are limited here. Honestly, I could just go cheap and put a sticker over the CEL and call it good, but then I can't visually know when there is another problem. This also applies when the CEL is always on, unless you go check for errors you don't know when faults start adding up. The 3.0l is a pretty reliable engine so it's not like 2.7t where you might have a CEL on so much that it burns out the cluster bulb. I typically scan for errors once a month via my OBDeleven, but I really like to keep my car running as problem free as possible.
That all said, I know the current battle on the B8 S4 platform has been IE vs 034, but as of lately I've heard more good things from from 034 customers than IE. Also I've really enjoyed the transparency and info 034 offers on their Youtube channel: https://www.youtube.com/user/034motorsport/videos
I'm going to reach out to them to make sure they offer a "test pipe" tune, and hopefully in the coming months make this CEL go away. If you run 034, please comment on your thoughts. Thanks all!