Dam,I did forget to mention ATF will clog cats..

I cant say if it did knock down carbon build up,I never took that engine apart.
But on MarvelMystery oil.I added it in with the gas like premixing,It worked good.. when I took that engine down,NO known carbon on rotor,or the moving seals apex/side/corner

But there was carbon on the springs,So I personally think it help either with the break down on carbon,or prevent more from coming.I got the car with 86k on it,and drove it till 110 used MMO for about 2 years..

Only down side I had,was when the gas level would get low,it just felt like it was picking up (deposites?) making car run a little rough.