Bmw e39, running rich, engine knocking sound?

you are being taken for a ride-the giveaway is the 'flush engine and changed oil(synthetic high performance)', engine flushing is a waste of time and money, you have an internal engine problem, a knock is never a simple fix-the last one that I ignored on a beemer cost me a new longblock, these are great cars, but when they unravel, they go down hard and expensive...get you car into a licensed BMW shop, STAT.