One of the member's here emailed me last week and I gave a detailed response. I'll share the basic of it here and tell you what we'll be doing.
First of all, we won't just make a catless pipe and sell it without knowing what it will sound like inside the cabin of the car. Since the ask is coming from the 1M crew we would want to make a pipe and test it on a 1M under the conditions that represent the most common denominator of the group, that might be stock axleback with a catless resonator-less midpipe.
Personally I doubt a catless, resonator-less midpipe is going to sound great so on first volley we'll more than likey incorporate the tuning baffle we engineered for our Street Series axleback for the regular 135i's. In initial development of that axleback the first test unit sound terrible inside the cabin. The drone spanned a good 2000 rpm range down where you cruise around town. I hated it, so back to the drawing board. We came up with a hand made baffle that is incorated into a small section of the 3" pipe and it elminated most of the drone. You went from a 2000 rpm range to a 200 rmp range that is almost non existant..with no muffler at all. So I'm thinking we'll use that technique and give this a shot. Don't hold your breath though. As easy as this sound there are many logistally bits that have to be done and we need to feed it into our fabrication shops schedule. We've had a 135i dual outlet axleback project that is over a year old and we are still working on it. Don't get scared though. The midpipe is a much easier build, but don't be looking for one next month. If you have a more immediate need I'd just order a normal MadDad midpipe which has already proven itself.
If you want more updates I'd suggest hitting Harold at HP Autowerks. Harold will be testing this new pipe on his 1M and will be able to attest if it is a worthwhile option since he already has MadDad resonated mid as a baseline.
As you guys can tell, I am not on the forum much these days. HP Autowerks carries the line and is very active on the forum and we'll communicate where we are at with them since they will end up testing this pipe.