2002 4.0 sohc, with engine running and you pull vacuum hose from the egr valve should the idle change when in closed loop,operating temperature. I have feeling mine not working properly,thanks

 

No, idle won't change.

EGR system isn't used when engine is cold, or at idle, or at Full Throttle

EGR system is used to lower the combustion temperatures when engine is under load, this reduces the NOx production that occurs at higher temps, and also prevents pinging/knocking on 87 octane gas.

Computer controls the vacuum at the EGR Valve using the EGR modulator, it is a 12volt valve the computer pulses, so it can open EGR valve a little or alot.
So there is no vacuum present on the EGR valve hose unless computer wants there to be.
There is a DPFE sensor(pressure difference sensor), that the computer monitors, this sensor tells the computer how far open the EGR valve is, it measures the pressure difference at 2 places in the exhaust manifold, as EGR valve opens pressure closest to the EGR tube will go down more.

 

Can this cause a slight ping under acceleration, if stuck or not working properly

 

Yes, EGR system is there to cool combustion temperatures when engine is under load, accelerating would be under load, this cooling lowers the NOx levels in exhaust.

And this cooling also prevents pinging/knocking as well.

Pinging is pre-ignition, air/fuel mix self ignites in the cylinder when compressed and slightly before spark plug fires, the noise is caused by more than one ignition point in the cylinder.
Octane is a heat rating, the lower the octane the lower its self ignition temp
Compression causes heat, engine under load heats up more.
9.0:1 compression ratio will usually run fine on regular 87 octane gas, above 9.4:1 you can start to get pinging on 87 octane.

4.0l SOHC has 9.7:1 so will not like 87 octane, what Ford did so you can use Regular gas is to add a Knock Sensor, when computer sees a knock it will retard spark timing so spark plug will ignite fuel before it can self ignite, knock sensors detect knock BEFORE you can hear it.
So if you hear a knock/ping then you could have a Knock Sensor problem, which is not uncommon on 4.0l SOHC

Your EGR system could be the problem but you should still not hear a ping/knock because of the Knock Sensor.
Try running a tank of '93 octane, pinging should go away and you should feel alot more power because spark is not being retarded.
If power is not greatly improved then knock sensor is bad so computer wasn't retarding the spark and thats why you hear pinging.

 

it runs very very well on 93 with a ton of power no not just a slight ping under load with 87 or 89 no knock