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!

Today is the day I get my S4 back. Michael at Apex Performance and Fabrication (also found on Facebook here) just sent me these pictures last night.... and all I can say is WOW, just amazing work. If you live in the PNW and need exhaust or other fabrication (they do lots of stuff) I certainly recommend this place.  

• Catalytic Converters used: MagnaFlow 53956 (affiliate link)

My initial thoughts of the sound? Yes it has some rasp, but the more I drive the more that seems to go away. So far I think I've put many 100-200 miles on it (video is showing zero miles) since I got the car back and every heat cycle the tone has gotten lower and less raspy. I will say this is much louder then before, I'm a little undecided if I like it or if I need to add some resonators back to it. Likely in a month or so we will have true idea of the sound and a update video to follow. Subscribe to my YouTube channel here.

 - Amazon affiliate links were used in this post

Well my passenger side cat (catalytic converter) cracked right before the flange that connects to the headers. It all happened when I would pulling away kind of hard from a intersection, heard a pop, and the car immediately sounded bad. Drove about 5miles home and captures this video of just how bad it sounds.  My guess is that during our snow storm about a week below that I hit some deep snow and it caused too much flex on the exhaust. Likely formed a crack at that point and just blew when I pushed the car hard. Oh well I knew I would going to need to do something with the cats if I ever wanted to go dual pulley. 

And just for reference this is how it sounded days before when I flashed the latest EPL tune update:

I had the S4 towed over to a Apex Performance & Fabrication. The plan is to take out the old cats, fab a test pipe from the header to the down pipes... and finish with new cats in a newly fabricated down pipe. The owner explained to me there is no point in trying to re-weld the old cats as they will just crack again. And we all know this is a common problem in this platform so that was no surprise. Anyway that is where it is now I will post again with some more videos of the sound changes (if any) once I get the car back. 

Following some of the suggestions found on the following thread, I decided to modify my existing stock exhaust to allow it to sing a better tune. 

https://www.audizine.com/forum/showthread.php/406948-Exhaust-Mod-Resonator-replaced-w-X-Pipe-(video)

So, I had a Magnaflow 11385 installed where the baby resonators are located, and straight piping where the mid muffler.

And here is a drive by, drive away, inside, and some reving all in one:

​As for my initial thoughts, it is near stock like quiet when cruising at 60 mph, no drone at all. Once you open it up it has a prrr like sound very familiar to a VR6 or VW R32 with out the the lower tones. The best part, if you drive it gently, it really is not much louder than stock. Not to mention from the outside, it still looks 100% stock.