95 nissan truck won't rev and runs rough

It Sounds like it is staying in the "cold start" routine. It also sounds like the diagnostic computer is not working right, because it must be rich and the O2 is not telling you a thing.

I would start by looking for a temperature sensor. You may have 2, with 1 being for the dash and the other being for the engine controls. You want to replace the temperature sensor for the Engine controls. This will help get it out of "cold start" routine.

Change your thermostat. The onboard computer does not monitor operating temperature.

Fuel pressure regulator. Have pressure checked.It could be forcing too much gas in each time an injector opens.

If you can not do this yourself, tow it in. At 2 mpg it may be cheaper to tow it than to drive any distance for repair. The Mechanics are going to need some gas left over in it to work on the engine.

Also turn on ignition and energize the fuel pressure, check for leaking fuel lines. Put on fuelcap locks if fuel drops when parked.

For this much of an extreme problem, I would like to know what you find wrong with it. I hope my solutions help.

Go up on gas octane to 89.

Back firing is usually an indication of a timing issue

The timing chain is most likely worn & jumped a couple
of teeth or the distributor was installed wrong,if you recently
had work done

you are SURE you have enough fuel pressure? like 60?

different airflow meter calibrations,do you have the z32 airflow meter installed?

Number of possibilities. See if you have any diagnostic codes stored. Could be throttle position sensor, coolant temp. sensor, hard to say. I would start with the codes. Does it start easy when warmed up, and run good? Boy, I just don't know.

try running a good injector cleaner thru it- sounds as if you have a(or a couple)weeping injector,
try LUCAS injector cleaner- works on my sonoma

carb automatic choke sticking closed or your float setting too high causing flooding engine.

black soot is a running rich condition it's getting to much gas not enough air .. 14-1 ratio air to gas your carb rebuild needs to be rechecked for sticking float..

Is the MIL light on on the dash?