It's similar to that. It can mainly be heard on idle. Kind of like a fan flapping on a piece of paper or something. At higher revs, it can barely be heard. Maybe the black oil caused the injector to become dirty? I'm thinking if i should have the injectors replaced, because of what you have said. Maybe that may be the problem. I'll see what can be done.
By the way, i'm at 91k miles now.
