Odd engine cutout problem

So, I have an 87 Comanche with an odd throttle cut out.
Specifics:
4.0L (Unknown year, not original, Renix)
AX-15 5sp (Suspect this is why the PO did the engine swap, Pukegoat died)
np-231 (also came with the swap, date code is around the tranny's)

It's still a Renix motor, it has three bolts at the intake rather than 4.
On to the problem,
When driving, in any gear if I give it WOT at above ~3K RPM then the motor just dies. If I let off the throttle it instantly comes back to life. If I am at 3/4 throttle the motor will go above 3K all the way to the redline with no problem. If above 3K at 3/4 throttle you jab it to the floor the motor will die. I've not determined if it's an ignition or fuel cut off. Since it only happens above 3K at WOT it's not something I can look at in the driveway. It seems like it's a fuel thing though, since I can goe above 3K at partial throttle. I think the ECU is cutting the injectors off for some reason.

THings I have checked:
TPS voltage: Within spec, .85 to 4.85
All electrical connections have been cleaned and checked for continuity with the ECU plug.
IAC has been cleaned.
TB has been cleaned

I just bought this truck, so in the past two weeks I've replaced these items:
PLugs, Wires, Cap, Rotor, Air Filter, Fuel Filter, Oil Change w/ Filter
I've changed the Tranny fluid, diff fluid and t-case fluid, I didn't see any wires hanging from sensors down there. I've pulled the negative wire a few times while doing tun eup items and it's made no change.
I've not yet replaced the O2 sensor, but it's on my list. I suppose that could be it, but it was my understanding that at WOT the renix ignores it anyway and uses the map sensor. Speaking of the MAP sensor I've not done anything with it but clean it's electrical connector. Should it be cleaned or maintenanced in any other way?
I appreciate any ideas, I've tried to be thorough, if you've made it through this much of the post you deserve a cookie.

Remember that the TPS is essentially just a variable resistor like a volume control on a radio, so one possibility is a bad spot in it. The calibration voltage can still be right, but if it momentarily drops out, it might cause that. If you can, you might try hooking an analog ohmmeter to it (power off, disconnected in this case) and see if the needle jumps or drops as you move the throttle.

I did check it with a sweep style meter and it seems fine. I may have left it out of the original post, but WOT works ok below 3K RPM. I can floor it in 3rd and it runs like hell until I hit that magic RPM mark.

just a thought.
I've been reading all I can find about engine woes on the forum and it seems as if the knock sensor may e the issue. I'm just not sure it would have such a severe effect. Is there anyway to bypass it temporarily to test this theory?

I am having similar problems....

When giving full throttle it just doesn't have all it's power. If I let off and mess with the throttle, then it regains a bit. Also when I am driving it will randomly just cut out without throttle change.

Roy,
I should have posted what happened to the Mj in this thread. After holding the throttle down and seeing if I could work through the cut out I ended up killing the MJ and had to have it towed. The problem was the fusible link that fed the ECU and the Fuel Pump Relay. At high RPM/High Load the circuit was cutting out power to the fuel pump and injectors. Something to check.

Awesome, I'll take a look at it. I just have to figure out where it is now.....

Maybe I can do a search and find a topic about it.

depends what year you have, I think they switched from fusible links to a big power distribution block in 91. Fusible links will all be attached to the starter switch, just behind the battery.