I've had it twice last year. 1st time I tried the Wynn´s stuff, Didn´t help. Then I tried the ATF trick. Poored a 1/4 of a liter of ATF in my engine. I then let it idle for a couple of hours so it was hot. I then revved it like a madman and hey presto the noise was gone. Changed the oil twice.
The second time I just gave it the beans, so thrasted it really. Pulled it to 6500 RPM, I never do this, but it did help. The vibrations at higher revs help to unclog the dirt.