@Sagerific95
The 93-94 EGR 4.0l was rated at 23.8 mpg and the 93-94 FEDERAL at 22 and change.
Ford chose to go in an odd direction with the changes Incorporated in the OHV 4.0 vs their 2.9 exhaust manifold. The 2.9's exhaust manifold inlets are nearly matched to the heads exhaust port outlets while the 91-97 exhaust manifold inlets are very oversized when compared to the 91-97 head exhaust port.
If a set of 91-97 exhaust manifolds are used on a 98 spec head, the dynamics are further exaggerated. This is not helping your exhaust flow/velocity. While I am not absolutely certain how much fuel economy this is costing your engine, it is another component in your equation.
Using a set of 98+ OHV 4.0l exhaust manifolds (or headers) may help you recover some lost efficiency; ironically, even stock 2.9l manifolds, with your build (or headers), will also offer improved performance but will require a minor adjustment to the EGR tube boss