its your exhaust donut...between the y-pipe and the mid pipe
my 07 did this AND my buddies 2010 M8 is doing it as well - no concern, just looks like hell on a brand new sled
i replaced the donut and it fixed it
maybe someone w a cat can chime in for you???
Just fixed mine,did the same thing brand new,Take it apart and silicone the inside and out side of the donut and your good to go!
High heat silicone(Canadian Tire)
Had the same problem with my 2009 Crossfire 800 the donut is your problem.
The worst is to clean the inside of your cab. The donut is a 3 min job cleanup well it a hour and a couple beers.
Yup I agree with the donut leak, make sure you use a high temp oil resistant silicon gasket material though. On the other hand, my 09'M8 was doing this also, and upon further inspection, the weld between the y pipe was cracked, so have a good look at this also.