Thanks guys... for the comments.
Yes actually my M5 does have the race exhaust but I do believe that Eisenmann and others have posted no gains via the axle back variety.
Tyler I seriously doubt Im running 650 at the crank---- I think there is less drive train loss with the DCT so its higher than the 560 factory number but not at 650.
2013 BMW M6 Alpine White
2013 BMW M5 Alpine White
2012 Audi R8 V-10 Ibis White
2012 Mercedes Benz C63 AMG Black Series Obsidian Black