I am making this thread to show specifically what is considered "core shift" I have a very prime example 99 B16A head. The pictures may be a bit deceiving, but the lip (where the dark part is near the valve seat) is very deep. the valve seat itself sticks out a good bit on some cylinders, this is only on the roof side of the port. The only way to fix this head it seems, would be add aluminum. Almost every gsr head I hae seen has little to none of this.