disconnect the electrical connector from the map or the vacuum line from the map (if applicable as in if the map doesnt go right into the intake like many newer vehicles), or both electrical connector and vaccum line?

 

Just the electrical.
1988 doesn't matter there is factory predetermined map ratio still when the pcm can't see it.
If you have a timing light you should check the timing, you have -3 to +3 to try, sometime just a tiny +1 more advance can make huge difference. All those pdf included.

 

I do have a timing light. Thing is that the truck was running great for months and all of a sudden it started doing this. Timing / dizzy wasnt touched. Nothing was touched. I also looked up a video of testing the fuel pressure on this 4.9l and it showed where the Schrader is. I looked all over 3x and couldnt see one. I figured it didnt have a test port Schrader because not all vehicles do. It was the first thing I went to do was check the fuel pressure so I'm kinda ticked off as I'm not with the vehicle and I've already been to it 3x testing stuff here and there. So on my next visit I'll test the map and the fuel pressure.

 

One thing that noone has commented on is when you pull the jumper connector near the icm that supposedly gives the ecm control over the timing, and the truck does the same exact thing the same exact way, does that not prove that when the jumper connector is plugged in and the ecm is supposed to have control of the timing that the ecm is infact still not controling the timing and therefore broken? I get ppl want to rule out fuel and air but this really feels like a spark issue. I dont know of anything else that can make the rpms jump around so quickly or cut out and kill the motor so fast. This isnt like if you block fuel or air it usually peters out. This is instant death like the spark gets cut off.

 

If you still can't find that port, that's normal for 1988. Many 199x cars are without a service port as well and simply add the gauge inline to the fuel filter outlet if it's located in the engine bay rather than the driver-side frame rail behind the front wheel like most fords.
Look below "installation" step 8, the fuel inlet at the rail connection, that should be where you need to add the inline adapter like this in order to attach a gauge. Look at the two pdf below for correct size.

 

So ilthe video I saw that showed where the Schrader valve is for the fuel rail was in fact where the one on this truck was located. Cant believe I missed it the first time. The fuel pressure was 52psi non running, 48 at idle and would jump to 60 when I revved the motor And come right back down to 48 and hold steady. I have found that the engine dies when you touch the throttle, happens after its warmed up.

I also tried disconnecting the map and i expected it to run like trash and it did, it did still end up stalling out like when the map was plugged in. It just wasnt as quick a death it seemed more erroneous as to when it would cut out and or die.

Any other ideas before I get a new ecm? Which I have thought it was from the first 30 minutes of my diag like a week ago.

 

So MAP is still good, and your fuel pressure is good.
There are still many possibilities I wouldn't get new ecm at this point. You can still check your throttle plate movement, your iacv might need a cleaning, a vapor lock and even ECT (engine coolant temperature) sensor, or a major vacuum leak somewhere.
You said you tested the TPS and you got 5V there is a lot more to test than just getting the vref. Find attached TPS_test.pdf below for you to retest.
Here is a list of diagnostic routines if you need to look at any in particular let me know the routine number it's from my Alldata software.

 

It'd be routine 205 or 207 I'd guess. Ive had plenty of cars run and drive with tps issues., Mal adjusted, broken, etc. I dont think thats it. I also don't see how the iac or blade adjustment would make the truck do what it's doing. Even if the iac is open when its not supposed to be, I'm opening the tb anyway letting in metered air via the gas pedal. Same with blade adjustment. It would be different if it stalls trying to idle or on decel but this is a cut out on acceleration and if you let off fast enough it will catch itself and idle again. It also only does it when warm so closed loop mode.

We pulled the ecm anyway to get the numbers off it and it said remaned on it. So we opened it up and it looks like its been worked on.

 

 

Do you have any kind of test equip like multimeter ?

If not , it may be time to invest in one, why?

With a meter you can obtain any codes that might be in the system. There are plenty of videos on how to do this.

With a code(s) you now have some direction AND can easily check fuses any time you want to do that.

That is my first suggestion and another thing you can check is the pick up coil in the distributor.
Don't remember if your dist has a vacuum advance which if it does, could explain the instant shut down when the advance moves the pick up coil in the dist. If there is a broken wire from the coil , every time the advance moves the wire in the circuit opens and engine can shut down because crank signal gets lost.

There is a DEFINITE procedure to remove the dist to replace that pick up coil and it should not be attempted until you understand the correct procedure.

The only $$$ you need to spend ,if you want to , is for the meter. We should be able to offer some guidance if you decide to pursue this route.