I had a friend of a friend who had a buddy that was a former BMW mechanic. It seems it was common for them to rebuild bad engines in the shop for trade in, used vehicles to resell them. He said they always had extra parts when the engine was reassembled and it seemed to not generate any cel or performance issues.
Ive known guys to remove the counter balance shafts to reduce rotating mass for the engine to rev quicker, it just runs a bit rougher, but I am sure a true bmw owner could feel a difference.
Never heard of a benz throwing a rod or loosing the temper in the rings, but vws are another story.
