I would check TPS(throttle position sensor)

It is the fuel injection equivalent of a carb's "accelerator pump", it tells PCM(computer) to add more fuel when you press down on the gas pedal, so you get instant throttle response.
But............you should get a code if there was a problem with TPS

Get a volt meter and set it for 20vDC
Use a sewing pin to pierce center wire on TPS connector
Turn on key, engine off
Ground meter and test voltage on center wire
Should read .69-.99, under 1 volt, throttle closed
Now open throttle manually and watch voltage, should go up steadily as throttle opens, no jumping or dropping.
At WOT(wide open throttle), it should read 4.5-4.9volts
Open and close throttle several times watching voltage

Free and easy vacuum leak test:
Warm up engine, let it idle
Unplug the 2 wire connector on IAC Valve
IAC Valve will close all the way and RPMs should drop to 500, or engine may even stall, either is OK, it means no vacuum leaks.

If RPMs stay up then there is a vacuum leak

Now there is an anti-diesel screw on the throttle linkage that some mistake for an "idle screw" and fuel injection can't use an idle screw, no Jets.
If RPMs do not drop when IAC Valve is unplugged then someone may have messed with this screw.
Turn it counter clockwise and see if RPMs start to drop, if not turn it back to where it was.
If RPMs do drop then keep turning screw until engine is at 500rpms barely running.
This also adjusts TPS throttle closed voltage so retest it

 

 

yes, bucking/hesitation issues are usually air/fuel mix related
When you press down on gas pedal air/fuel gets instantly Lean, MAF air flow/voltage increases slowly so there is a delay, TPS gives computer the "heads up" to add more fuel instantly

Cold or warm
Dirty MAF was common issue on 4.0ls
Vacuum leak
dirty fuel filter, causes momentary pressure drop under acceleration
TPS is long shot, but not no shot, because it is monitored

Cam position sensor could cause it, but again a highly monitored sensor

 

 

Could it be in limp mode? I did watch a ranger with that happening one time, but it was more like it fell flat on it's face rather then bucking. But in park it would act normal

 

 

Plugged up exhaust maybe.

REV engine while someone feels tail pipe flow

 

 

 

Yes Ford Coil Pack coils should be about 1.6 ohms, 1.3-1.8 was the range I think

Yes all 3 should be within the same range.

So that one coil has a short in the "coil" of that wire, so when you test the OHMs it is traveling thru a shorter coil of wire, so has lower ohms.
This does 2 things, it powers up faster but not as much, and it releases a spark sooner and weaker

Yes, it could cause misfires issues under load, i.e. when air/fuel mix gets Rich you need a stronger spark

The coil is not broken, just out of spec so wouldn't generate a code most likely, and it is an unusual occurrence.
I read about early 2000's 3.0l Rangers having coil pack issues, nothing about 4.0l coil packs in any year

 

 

If possible go to auto parts house with your ohm meter and test a new coil pack, just to see.

Spark plug wires can't be hurt by coils

Have a look at this video: youtube.com/watch?v=c1zhgsnyZWw

Confirms coil pack problem

 

 

0.9 yes

The coil STILL WORKS so engine could run fine and then not run fine, when it heats up OHMs may go above 1.1 OHMs, so works better, or not.

This is not an ON/OFF failure, which is why it has been hard to track down.

 

 

 

In Park or Neutral all fuel injected engines will have a REV limiter active, usually 3,000rpm is max.

 

 

At this point I would spend the $30 on a Bluetooth OBD2 reader so you can watch LIVE sensor levels while engine is running and even while driving.

Can't recommend one over another
APPs are free or $5

If possible get an extension cable with it.
These OBD2 units work on ANY vehicle sold in the US or Canada since 1996, so not a Ford thing, all vehicles sold were required by law to use OBD2 protocol in there engine computers
The extension cable will fit in tight places so you don't have to remove panels to plug the unit in directly

 

 

Order one on-line or thru Walmart or other stores

You seem to want to change sensors which gets expensive, and if it was a sensor issue then it would set a code, and you said shop saw no codes.

What the LIVE DATA tells you is what the computer is "seeing" at the exact moment of any problems, this tells you if any specific sensor might have an issue, this is something a mechanic can't spend time doing it would be way to expensive for the owner of the vehicle.

Ported Vacuum leak
From the MAF sensor on the air cleaner over to the intake is the Ported vacuum plenum(air tube)
Low vacuum at idle, higher vacuum as RPMs increase
Any leaks here means not all air is going thru MAF so same issues as any other vacuum leak.
On this air tube is also the Vent tube for the PCV system.
At idle PCV Valve should be almost closed, so low vacuum in engine area(valve covers, oil pan) and air tube.
As RPMs increase PCV Valve opens more and vacuum in engine areas increase, as does Ported Vacuum.
So there is a balance
So it is important that the air tube has a good seal at both ends and no cracks, also the Vent tube and PCV Valve need to be sealed and working