Ford Escort - Rough Acceleration

Any codes given? Pcm sets the mixture, using all the inputs and designed programs, you can't reset it. If it is indeed misfiring, there should be a code given, any chance the check engine light flashes on and off?

Plenty of issues that could cause surging, most are not diagnosaible by the average driveway mechanic. You sais you replaced the pcv system because it melted? What is that? Make sure it is hooked up correctly, check all electrical, vacuum, any connection you can see. Evap system could be causing issue also. On some of these cars, if you refuel while the cart is running, you can damage the evap system by drawing liquid into the system, it's rare though, but still is a concern.

Ford has had a problem with the Mass air flow sensors becoming dirty on these models that can cause the symptoms you describe. However, just by symptons I am not going to recommend you replacing a $150+ part.
I have heard of people having success by cleaning these sensors, but one mistake and you will have to buy a new one whether it was the problem or not.
If you decide to try and clean the sensor, you will want to use a electrical cleaning spray. It must be quick drying and non-residue. You do not want to blast this sensor. There will be 2 very tiny wires in the air stream of your intake. You only want to lightly spray these wires only. If you get the spray too close, it can break these wires and you are replacing the sensor. I would try and lightly spray these wires to try and dissolve the build up on them. The build up will be small, and the cleaning will be small also. Allow plenty of time for the chemicals to evaporate before attempting to start the car.
Usually you will get a too lean code latched in your computer, but maybe it hasnt gotten to a point inwhich the computer has picked up the fault.
Typically when I hear complaints such as yours, I think plug wire, or something in the ignitions system breaking down under a load. Another option you have is to buy one coil pack. Replace one of your coil packs and drive it. If not improvement, install the removed coil pack in another position. Continue until all coil packs have been tested. If after rotating them all thru the new coil pack, and the problem is not fixed, the only remaining ignition components are the PCM and the crank sensor. Both of which usually cause the car to just die and not start.
Good luck and if you dont have success, then you may have to take it to a mechanic and have them test it out on a diagnostic machine.

Well, have you had your injectors checked? I would turn to the fuel side and check the fuel pressure and injectors for proper operation.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

https://www.2carpros.com/articles/engine-surges

Engine hesitation can be caused by the following:

Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires