Changing Distributor caps and Coils can't hurt doesn't cost that much can only help for future. Other than that I would find a good shop that is recommend by the local BMW club as knowing V12s and is affiliated with them and have them put it on the diagnostic machine and get their opinion. Opinions don't cost a lot, see what you can come up with and if you go to a dealer, if they say lets try this, then tell them as has been suggested before, tell them that if you try what they say, if it fix's the problem fine you'll pay for it. If it doesnt' fix the problem, they have to remove whatever they did and not charge you until they find the problem. Hey, they are the experts right? Good Luck, Kurt