Problem I cannot solve. Ideas?

Re-update: Found some similar comments of other TPI owners. Hose in tank was split, apparently TPI pump is more than capable of producing pressure with a massive leak. Hose was almost ripped in half. Explains hot fuel rails, predictable loss of power under heavy load, seeming "vapor lock" after heat soak, etc.

Update: Got a fuel pressure tester from Autozone, 25PSI pretty much all the time. Just a bit over half of what it should have. Hoping it's the pump (have a spare, fairly easy to change), will test regulator tonight to verify. Hoping it's not the factory braided steel lines coming apart inside from the ethanol.

I can't live with it anymore. I've got to do something. Up until right now I thought my MAF tuning skills were the problem, now I'm thinking that's not it.

Setup: 1989 6E MAF/TPI, Ford 24# SVO injectors, Vortec heads, Manual trans, etc. I'd say the setup has at best 30,000 miles on it since I put it together, but that's a lot of used parts, short of the injectors which I bought new. Pickup coil and module are both "new" (failures a couple years back), not that that means anything now.

Been having an impossible time getting rid of a "tip in" stutter. Tried everything I know, got better, but has never gone away. Causes a large issue trying to get moving with a ~1500lb trailer attached, as it just backfires and stutters. Really slipping the clutch helps, but is not what should be needed. Probably a bit undergeared, but not as bad as the tip in problem would indicate. Were this the only problem, I could deal with trying to fix just that.

The REAL problem, is that at some point on a warm/hot restart, the engine will start to chug, RPM's will fall below target, and manipulating the throttle may or may not increase RPM's. More backfiring, excessive engine vibration from misfire, etc. Exhaust so bad it makes you ill. Heated O2 reading in the .1 range while this is going on. Eventually I might be able to get the idle RPM's up to the 3K range by pumping the pedal, where it starts to smooth out, but if I let off, either it will go back to a semi-normal idle, or it will idle poorly, but either way, upon trying throttle again, it starts to chug and misfire. No CEL until the engine dies, of course. At some point, by sheer luck, I MIGHT be able to get the truck moving, and at some random time, it just clears up and runs fine. But I can't trust it, and when acting up, I am literally stuck right there until the stars align and it either gives me a small window of opportunity, or I just sit working the throttle until RPM's get high enough I can slip the clutch and start it rolling. When it was running bad tonight I even changed the timing map in +/- 10* increments, no change that I could discern except to make it worse. Clear flood helps it start in these instances, a bit, but once started, horrible idle immediately starts again.

Because I'm so far from a stock setup, my tune is a long ways off from stock too. This time I got fed up, shut the truck off and went back to a stock bin, the 1989 APYP, figuring if the tune is the issue, going all the way back to stock would make a huge change. Fired it right back up, same exact issue. My timing and fueling is WAY different than the APYP so I really expected the problem would be much different if it were a tune issue. I've got a couple spare '165 ECM's, I've swapped them before, issue is still there.

Somewhat interestingly, tunerpro/emulator started giving me issues burning chips tonight (failure to erase or program) but that went away after a couple tunerpro restarts. Because I had a "bad" chip in the ECM, I said screw it and started it with the CEL illuminated. Ran pretty much identical to how it did with the PROM in it...terrible. It was actually very, very similar.

It will also die if I don't keep my foot in it now when it's acting up. Even a restart will immediately die if I don't give it throttle.

Tonight, prior to this happening, I let it idle up to about 185* (195* t-stat) then took it around the neighborhood a few times checking my AE changes. Drove pretty good, better than it has for awhile. Started/stopped engine a few times as it was warming up to try and induce the problem, see if I could narrow down a temp range, but it started fine each time, up until this issue, after it got good and hot.

I had a couple of bad stock injectors way back when that initially caused me issues (no hot restarts, ran fine otherwise) and is the reason I went with the SVO's, but I'm not entirely convinced this too is injector related. Being intermittent, I could probably carry a multimeter around and check them when it is malfunctioning I suppose.

Anybody got any ideas? I am never one to just throw money at a problem, and I wouldn't even know where to start throwing money at this issue.

Thanks for anything, this is really making me despise the thought of using the truck at all, and of course I will have to drive it Friday. If I didn't have to stop a couple places, I'd be ok!

Edit: Now that I've calmed down a bit, I'm thinking fuel or ignition are the two issues here. Intermittent but based on heat, so something that is not working after getting warmed up. It would seem unlikely to be fuel outside of injectors, but checking fuel pressure should indicate an issue, if done while it's acting terrible. Ignition is going to be pretty tough as an intermittent, but swapping all the components out can be done, as I have spares. Only options for injectors are to send them out for service, or get lucky and get a bad ohm reading when it's acting up. Any other potential diagnostic ideas I might be missing?

Ohm'd the injectors cold and after running. Started to run poorly, but not as bad as it can. Rough idle, hard to increase RPM's, but could still move. Anyway...ohm readings =
Cylinder)cold/hot
1)15.6/16.3
2)15.6/16.4
3)15.8/17.2
4)15.6/17.9
5)15.7/? (couldn't get to in time)
6)16.2/16.6
7)15.6/? (couldn't get to in time)
8)14.9/16.6

Nothing out of the ordinary there IMO, but again, it wasn't acting up as bad as it normally does. Definitely seems to be heat related, only turning truck off an letting it sit triggered the poor idle. Going to have to take the multimeter with me to test again when really bad.

Also noticed the fuel rails were too hot to touch for any length of time. Measured them with the cheap multimeter, 149*. Seems way hot to me. The intake measured 158* near the t-stat. This was after a few minutes of potential cool down.