From my understanding you can watch the cobb YouTube video or one on their site (http://www.cobbtuning.com/BMW-335i-xi-i-xDrive-s/1200.htm) you should be able to log your car with your cobb and look for a misfire. The video is for replacing.
Just a suggestion before going through the disassembly.
w/ -= VRSF 7" FMIC =-
-= Cobb: Stg1 +FMIC Aggressive ST =-
Next To Do: JL xd600/6 AMP
"If you're not 1st, you're last" -Ricky Bobby