I think the 2008 328i's have the same problem but I am uncertain. Regardless, as you all know, no one on the face of this earth makes tubular headers for the 2009 328i's. I've asked numerous experts and searched for months with no luck. I'm attempting to get a local speed shop to entertain the idea of using my car as a mock up and then produce them. At this point I have no idea of cost. If I can show there is a market out there maybe I can get these gents to bite. Right now they are in the "thinking about it" mode.
I have an LET ECU flash but it is being stifled by a "Service Engine Soon" light which, I'm being told, is probably canceling out the flash due to a cat delete I did. See below dyno and pictures. Darker brown plumbing is where the cats used to be. I gained 14 HP by just removing the cats. I bet I could get another 10 with real headers. Also, I have people working on the light as I type. Warning, if you want noise remove your forward cats!!