IAC valve

What symptom are you trying to solve? The engine computer will detect an electrical problem with that valve. It does it is major move when you turn the engine off, not when you turn the ignition switch on. I have never heard of anyone removing a battery cable as a test, so I would not know what to expect or what "normal" is.

Be aware you are going to have a hard start/stalling problem due to idle speed being too low. That is a normal result of removing the battery cable.

Inspect the throttle body to see if there is some carbon in there that the valve is hanging up on. That valve retracts when you stop the engine. That sets it in the open position to provide the nice "idle flare-up" to 1500 rpm at engine start-up. The computer will slowly close the valve in about three to ten seconds. If you have a high idle speed after disconnecting a battery cable, it is not due to that valve. Look for a vacuum leak.

Next is to look at the IAC "steps" with a scanner. Normal for a properly-running engine is about step 32 out of a total of 256 steps. If you find it on step "0", the computer has not relearned "minimum throttle", and is not opening the IAC valve at all. You have to drive the truck to meet the conditions for the relearn to take place before the computer will know when it has to be in control of idle speed. To meet those conditions, drive at highway speed with the engine warmed up, then coast for at least seven seconds without touching the pedals.

Once minimum throttle has been relearned, if you find the IAC on a real low step number but idle speed is too high, the computer is trying to lower idle speed, but without success. That is almost always due to a vacuum leak.

It should not move when you turn the ignition switch on. You just confirmed that. If you tug really hard, you can pull the pintle valve out of the IAC motor. Install it that way, then if idle speed is too high when you start the engine, it has to be due to a vacuum leak. You may need a smoke machine to locate that, but a leak that big should be easy to find by pinching off various vacuum hoses. The computer will not retract the valve unless it needs a higher idle speed

You are going to have to use a scanner to see what the engine computer is trying to do. That will also let you see all the other sensor readings the computer is responding to. Most scanners will have an IAC test that allows you to raise engine speed in 200 rpm increments up to 2000 rpm. If that changes engine speed, the IAC is working properly.

Also, remember that just driving the truck will not initiate a relearn of minimum throttle. You have to coast for at least seven seconds. The computer needs to see sustained unusually high manifold vacuum to know when to take a reading from the throttle position sensor and put it in memory. And if you disconnect a battery cable again, then reconnect it, minimum throttle will be lost from memory, and engine speed will be too low. If it is too high, it cannot be due to the IAC position because that entire circuit will not be working yet.

Nope. The only thing that can happen at times is due to the momentum of the exhaust gas flow, between the pressure pulses there are pulses of, in effect, vacuum, and those can suck in outside air. The unburned oxygen gets detected by the front oxygen sensor as a lean condition. The engine computer will try to adjust for that by commanding more fuel. You will have a rich condition and you might smell the unburned fuel at the tail pipe, but no matter how much fuel is added, there will always be that unburned outside oxygen being detected as the lean condition. That can cause poor fuel mileage with a diagnostic fault code of "running lean too long". Oxygen sensors only detect oxygen. They do not detect fuel or mixture.

This does not happen real often, but when it does, the leak is almost always right in front of the catalytic converter, not next to the cylinder head. I do not have a good explanation for that. When you have a V-8 or V-6 engine, the clue is the lean fault code is for only one side of the engine. A lean condition caused by an incorrect sensor reading, (other than the O2 sensors), would affect both sides equally. Even a vacuum leak can affect just one side when it is near one cylinder. Some vacuum ports are near the middle of the intake manifold, then a leak there would affect both sides.