I changed the Air Temp Sensor, and drove 45 miles, with no improvement in gas mileage.
I guess I'm going to have to pull the intake off and take a look at the plenum, anyone have any ideas on how long it will take, and what all needs to be taken off?

 

since your truck is a dodge, you probably do have a leaking plenum; but, its my opinion that a leaking plenum, by itself, does not kill your mpg. a leaking plenum is a vacuum leak, which causes a lean condition, oil loss, possible cat contamination, etc. it doesn't cause a super rich condition or bad mpg.
checking and fixing your plenum is a good project, but its not going to fix your mpg.

your report of black smoke and rich smell, and already replaced O2 and already removed cat - point to the things which deliver too much gas - injectors.

i would put in nice new clean spark plugs, drive about 50-100 miles and then check them. the dirty plugs might indicate the injectors with a problem. if you can't get any other info, just get a new to you set from the junkyard and either swap in one side at a time, or all 8 at once. you can also test yours with an ohm meter, looking for i think? 68 ohms across the pins when unplugged from the harness. see if any of yours are different from the others...

 

Alright I will replace the plugs probably tomorrow, and see if i can find a set of injectors from the junk yard to replace the dirty ones.

 

My guess is the ignition coil. I don't think I saw that on the list of things done.

 

The Ignition coil can cause that bad of gas mileage?

 

hmmm never thought about it but possibly

if its not getting enough power it could cause something else to work harder, possibly the injectors, and they are dumping fuel......

just thinking out loud......not sure if this can be the case

 

i don't think so.

 

I can't remember, does the fuel pressure regulator up front or on the tank in 94. If up front could be suckin' fuel . and still keep up fuel pressure. i

 

Regulator is back on the tank. We have a returnless fuel system...... Too bad.

 

then it has to be injectors or injector driver in pcm. He said he replaced pcm. I suppose it's possible to get a pcm with same problem, but i think if problem still shows no change at all after pcm change then it points to injectors. I would think. I'm just a dum ol, ford mechanic today.lol