I definitely got good results with the AR-CS on my 2010 bike. But to be honest, the 2012 runs just as well in terms of mid-range, and I just have a plain full Akrapovic system with the long can. Not much louder than stock at full throttle. Whatever they did to the stock bike for midrange for the 2012 model year carried over to the exhaust's performance as well; I clearly recall a massive torque hole in the midrange of the Akra system on the 2010 bike.
I'm curious if shorter systems have more top end (Austin Racing, Arrow Evo2), and wonder if BMW runs the long Akra systems on the factory race bikes for performance reasons, or to meet loudness regulations....a stubby Akra system was tested but only used for a couple races.
2012 S1000RR, sapphire black FOR SALE
2015 Ducati 1299S Panigale
2014 Ducati Multistrada Granturismo
2011 Ducati Monster 796 ABS
2000 Ducati ST4 (sold)
2010 S1000RR (sold)
2007 F800S (sold)