I don't remember the downpipe he had but he had a milltek cat back. I had a Invidia v1 catless dp. What I traded was a Cobb midpipe and turbo xs rfl axleback. My guess is that is what this is still. Maybe that solves the dilemma your thinking of?
I do remember the Cobb midpipe wouldn't work with the milltek axleback. So we traded catbacks and didn't have any issues.