Look how horribly awful the bend from the head to the catalytic converter is. If someone made that bend better shaped in favor of exhaust flow, you could pick up some power. On the engine in the BMW E39 M5, it had terrible exhaust manifolds that were like that. They were just log manifolds like you find on a really old American V8. We made headers and were able to gain nearly 40 horsepower. I haven't had the chance to get under my car to look at the exhaust manifold. I'm not at work temporarily so I can't put it on a rack. I wonder if you could just make an easy bend, shift the catalytic converter down a little bit, and pick up some power. This is assuming the K24Z7 is the same layout.