Sorry, totally baffled by the results

 

Can you at least tell if it sounds like an IAC problem or does it sound like something else is doing that?

 

Thats what has me baffled
The computer is not reacting to RPM changes like it should, but it is following protocol in full voltage for startup and then lower voltage after startup for idle
And IAC Valve is responding correctly for that

I can't see the IAC Valve itself effecting voltage that the computer is setting for idle, computer just checks for 12v on the grey wire from red wire with key on, which means IAC Valves 2 wires are connected to a solenoid, so no Code would be set
After that computer starts to pulse grey wires ground to control voltage and IAC Valves position

Maybe there is a voltage Range in the computer that I have never read about, i.e. max voltage engine running is 10v, so when RPMs drop computer can not send more voltage like it can with engine off for startup, but never even heard of that type of Range on IAC Valve computer control

I don't think Motorcraft or Hitachi IAC Valve will help from the tests you did, but might, its a roll of the dice

 

I'd rather try other things if we don't really think it's the IAC since a genuine motorcraft/hitachi one is about $60-80 when I checked. Not sure if this helps point to something, but ever since I messed with the anti diesel screw and put in the different ECU, I'm now getting 7-10 MPG city down from 12 MPG city. Didn't measure the mpg after putting in the new ecu before messing with the idle so not sure what caused that. I still need to get around to testing the fuel pressure. I noticed I seem to be idling at 700 rpm instead of 650 in drive now. My idle walks a good bit still and still have the issue of seemingly choking on startup. I noticed it smokes a lot from the tailpipe, more than I feel it should. The video I attached was when it was I think about 40 degrees and you could see your breath, so I'm sure some of the smoke is just because it's cold out, but it's still more than any other car I've seen at this temp. I attached a video of the idle walking, the idle surging a bit on its own, and how it kinda struggles to fire on startup. Like you can hear it firing and running but not fast enough to let off the starter without it dying. It starts after usually a few seconds of that though, it started faster than normal in that video.

Just trying to fully show what some symptoms are in-case it helps.

 

2.9l should be in the 15-17mpg, so yes, running Rich and smoke out the tail pipe, spark plug tips should be dark as well confirming Rich running

How old is the O2 sensor, if over 12 years or you don't know change it
Air fuel mix is solely based on that one O2 sensor, so it has a lot of power, lol

Computer uses MAP sensor, temp sensors and RPM to calculate air/fuel mix but changes that, completely based on O2 sensor feed back
Spark plug tips will tell you if O2 sensor is accurate

Rich running is less power not more power, that could explain the drop in RPM when "in gear"(load on engine) but not the lack of response by PCM to raise it back, still a puzzle

ECT sensor, 5volt, 2 wire temp sensor, sets Choke mode and then no choke once its heated above 150degF or so
Should have a black/white wire and green/yellow wire
You can voltage test it, 5vDC
Ground meter
One wire should test as 5v, black one, or can be grey/red
Other wire 3v or so cold>>>goes to computer
Then under 1v warmed up
Key on, of course

The 1 wire Temp sender is 12v, only used for dash board temp gauge, red/white wire usually

 

The O2 sensor is only a few months old (Bosch one I think) and so is the connector for it. I found that the old connector touched the exhaust and half melted so I just put a new connector on. I remember when I replaced it, it changed nothing so I'm not sure if the old o2 sensor and wiring was working fine still or if I messed up the connector somehow when putting the new one on. I made sure to connect the wires in the right places though, plus it's only 3 wires so it's a bit hard to screw up.

I also replaced the MAP sensor but it was the cheapest one on Amazon that I could find so it's probably not very good. Though I remember that also changed nothing when I replaced it so I may just want to throw the oem one in there and see if that changes anything.

As far as the ECT sensor goes, I just checked and that one has two wires for me, one green, one black.
also, the ECT is brand new too, but I tested it just in-case and it started out at about 3v, I drove it around the block to get it fully warmed up and then it sat at 0.775v so that looks to be good.

The truck feels like it has plenty of power to me while driving, but it's ran like this since I got it so I don't know what it's supposed to feel like. I don't have problems getting up to speed or anything though/

Like I said before, It goes to 500 for a split second then to 700 when shifting into drive. It just seems like it's not jumping up enough since it's supposed to idle at 800.

Edit: Just this morning I tried to start it and it did the barely running thing while turning the key for a solid 10 seconds. It took 3 tries to get it running enough to let off the starter and even then I had to rev it up to keep it running. Smelled like raw gas really bad

 

Finally got a fuel pressure test. After it had sat for a day, I turned the key to prime the fuel pump and I only got a couple PSI. Every time I turned the key off and then back to the start position, I gained a few PSI. After I started it, it idled at 32 PSI, then jumped to 33 PSI right when I turned it off. It went down to 31.5 PSI after sitting for 2 mins, then 31 PSI after sitting for 10 mins.
After it had been run once, turning the key to the start position jumps the pressure to 41 psi quickly, then it falls to 39 PSI after a couple mins.

Edit: I attached a video of what it started doing on startup a day or so ago without changing anything