You may find that the exhaust manifold isn't lining up correctly with the ports in the head. I have had several manifold and head combinations where this is the case.If you are using the 3 piece intake/exhaust gasket. bolt it to the head, and then tape all 3 peices together. Now lay the gasket on the manifold and see if the ports line up. You may have to elongate the front and back mounting holes. I have also have had to install a spacer between the exhaust and intake manifold where they bolt together for all the ports to line up correctly with the ports in the head.
gmc-is-me
