The main reason why on my build I am not using KB pistons is the design promotes carbon build up on the ring lands.Seems to be just a bad design.I spoke to Mahle some more to find you can run those pistons at 4.029 vs 4.030,one thousands tighter that limits or eliminates cold forge piston slap because of the coating.One tip they gave me was to NOT use anything like carb cleaner to clean the pistons before the install of them.That kind of cleaner lifts off the coating.Of course they are making claims the coating last for the long term where on another thread I had concerns posted.The piston/ring design on the Mahle hands down seal without any carbon build up.They also told me they don't build cast pistons or pistons without the coating.Yeah I think in this case I found the age old saying.............."You do get what you pay for".The Mahle of course costs more.