If it is a failed MAF it generally will run better. Might not idle correctly but certainly drivable. Easy to change as well. It could be anything, but I always check the easy things first if you don't have access to a code reader and someone to interpret it. MAF failure is pretty common and having experience in very cold climates, I know for sure many us BMW owners have that issue. Also check to make sure the airbox is tight and fitted properly.