http://www.realoem.com/bmw/showparts...38&hg=11&fg=15
Replace the entire oil separator system and all piping, not just one breather hose. Intake leak allows unmetered air, resulting in poor running. Check adaptive trims (part throttle multiplicative). If positive by more than 5-6% on both banks, it is having to add fuel to keep the air-fuel mix correct.