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.