5.0L feels under powered

[explorer4x472]

My 93 Explorer has a 95 5.0L HO engine. When I got it, it ran ruff. I have replaced the spark plugs, put on 9mm Ford Racing wire set, MSD coil, MSD cap & rotor. That made a big difference already. The air cleaner was some wierd carb air filter set up and I replaced with the factory air box and new tube to the throttle body. The engine does have a set of Ford Motorsort headers, custom made exhaust ( about 3" diameter ). The previous owner never put 12v key on power to the o2 sensor. I have done that know aswell, I have been told my catalytic convertor needs to be replaced because they full of fuel. Can that be the problem? The truck rides on 35's and has 4.10 gears. Is it just me or can anbody give me any ideas.

 

[Tbars4]

no codes??? the cat is my bet as it will get plugged, but you should also be losing milage...running the 35's with 4.10's is not helping much either...:scratch:

 

[explorer4x472]

The codes that came up when I got it first scaned were for no cooling fan ( have a flex a lite), EGR codes ( EGR valve not connected to manifold) and O2 sensor not heating. I am getting about 15 mpg combined city/highway driving. I am going to replace the O2 sensor cause they maybe carbon up. I will be replacing the gears with 4.56 soon.