He is using yang chakra not yin, yin was sealed by MinatoKyuubi cloak mode is the term for when he is using the Kyuubi's yin chakra. When he was fighting Orochimaru and Pain, he was using the chakra and going berserk. After Naruto defeated the fox, his new form is refered to as the Kyuubi Cloak Mode. That's what I was refering to.