I think we figured out where the exhaust leak was. We dropped the exhaust manifold to find this. Those were gaskets from the Kinugawa manifold. They looked good, but were actually garbage. So I guess we know that both oil lines and gaskets leak from Kinugawa. :/ Unsurprisingly the 12 year old OEM gasket between the header and up pipe was a little rusty, but completely fine. I will be replacing all of these gaskets with new OEM gaskets.