Re: 4.0 head swap exhaust manifold
There are two types of manifolds, YJs and some XJs have a center collector. When you get the mpi up and running, it will run lean until the computer learns it's new environment. And when you run lean this manifold will overheat and it will crack, no ifs. There is an XJ manifold that has a rear dump it is a lot less prone to cracking, the only down side to using this manifold is you will need to get a custom bent front pipe to go from the manifold to the cat(any exhaust shop can do this fairly cheaply).