I think you are talking about the exhaust manifold. My stock manifold cracked and I replaced with an ATS three-piece. (99 Dodge 24V) I did not hear any claims of performance gains when I replaced the thing, so it was surprising to me when I drove it and noticed that the turbo spooled up quicker coming off the line. It was noticable. I cannot say that I notice much additional power, overall, but I am sure it flows better and provides a little extra power. It is a well-built manifold, but is a bit pricey.