Sounds like you want race exhaust sound. Who doesn't?
Based on videos only the Akra slip on combined with Dinan x-pipe sounds pretty darn good. Or just get an Eisenmann Race.
2011.75 Jet Black e92 ///
M3: ZCP|6MT|BB interior|Turner Motorsport black pedals|IND
Edition Cosmetic Package |LUX 5K|35% tint|clear-bra|Vorsteiner GTS-V diffuser