I'm in contact with the people at Supersprint, i think you all know this brand and the quality of their products.
They're working on the the exhaust system for the R56, they have a complete system from the downpipe to the tip, both in kat+silencer and straight pipe versions. It's still a prototype, production will start in a month.
http://www.clubminitalia.com/vari/supersprintr56.jpg
The problem is, I said them about the Milltek system, actually the only complete one, and they told me it's a lot of crap. They don't have a rolling road at Milltek and the increase in power is totally hypotetic and optimistic.
They had very little increase with their system so the R&D is working on the pre-turbo headers, to see if they are the problem. Maybe it's not possible to have some good hp without touching the ECU!
More info soon...