Supersprint can be found her
http://www.turnermotorsport.com/BMW-...and-parts.aspx
And Remus is another option. Bavauto and beemerzone both sell Remus for our cars. I would be curious to hear how it sounds. Supersprint is top notch in terms of quality and sound. However, I haven't been able to find msporT rear diffuser required to run dual exhaust.