I'm certain the issue was in the ignition curve given it's tied to the EZL.

As for ports and what fits the 2.6 and 3.0 ports measured the same. We had a 3.0 manifold on a 3.0 in this car at one point and it fit but the egr blockoff was ugly and extra points of failure.

The air cleaner has never fit right on this car. The base is bent and that's an item on the todo list.