1998 GMC Jimmy engine keeps dieing

I did when I replaced it about 6 months ago, but since then I've put less than 1000 miles on the truck.
How would that make the truck just turn off and then start again an hour later after it cools off. And not right away. Plus the pump is priming everytime. As it is suppose to.

Cleaned MAF last night and reset the ECM still no luck, doesn't seem like it's going to die now but it stumbles in park while accelarating and while trying to drive.

As of today sat the 12th. I checked my plug wires to make sure they were connected still, took the egr valve, and blew out the build up, changed the egr valve with one off my other blazer. Drove it around thought it was ok drove it for 20 minutes beating it up. Ran great like new again. Thought everything was great and it was fixed, bout to shut it down and decided to wait till IAT got to 100 degrees or over. Since that's when it seems to mess up. It hit 102 degrees so I shut it down, restarted it worked fine but as soon as I stepped on the gas it would miss and act as if it were goin to die. Still stumbling and hesitating. And now won't start again. It seems to do this as soon as I hit over 100 degrees on IAT. HELP!

Ok just went back outside after letting it set for an hour. IAT is now reading 85 degrees when I started it. Started right up ran fine again, temp for IAT went down to 70 degrees runs great. So what could cause the truck to run like crap once it's at 100+ IAT?

As of today I've swapped parts out of my 2000 blazer, the ECM is good, maf is good, map good, TPS is good, IAT is good, coil is good, collant sensor good, ICM is new and good.

But I just installed a new fuel pump like 8 months ago or less than 1000 miles ago.

Ok so went out to start truck started up fine. Checked the fuel service line, fuel sprayed out when truck was running. Truck died no fuel would spray when pressed in key was on. Is this how it's suppose to be? Or somehow could my new pump be overheating or shorting out?

So ran truck tonight without airfilter. Same outcome, although tonight IAT never got to 100 degrees only up to 86 degrees. Still after about 40 - 45 minutes of idling and alittle bit of 15 mph driving around parking lot, engine still just turns off. I say turns off cause no stumble, no hestiation, no sputter just dies nice a calm like I shut it down. What would cause this. I've been debating weither or not to take it to a chevy dealership for a dign. But they told me if I'm not throwing codes then the diagn. Won't really help. So i'd hate to just waste $100. Plus I don't trust other people working on my vehicles. Plus I'm a pretty good mech. I build hot rods and cars in my spare time. But this problem I just can't seem to fix and every other car person I speak to can't put there finger on what this problem could be. Nothing makes sense. Lets start fresh. Truck is a 98 jimmy 4.3 W vin 4x4 2 dr with 134000 miles on it. New: battery, alt. ICM, plugs, wires, distr. Cap, rotor, K&N airfilter, running proper oil, new high flow cat, flowmaster 40 serious exhaust, new PCV, cleaned EGR valve, cleaned MAF, fuel pump, fuel filter. I seafoamed the engine and I run techron fuel cleaner about once a month or every other month. Also run lucos in the oil.

Before the engine shuts off, the truck runs strong as hell, like new, MPG are great. Right before this problem truck was at 180-200 miles with over half a tank left. With mainly city driving on it.

Took to dealership they say fuel pump. Wanted 1300 for it and labor. So does anyone know why a new fuel pump would work until truck warms up then drop to 44 lbs. When it was running at 65lbs. Or do I need to just replace this pump again. It's new like 7 months old with about 1000 miles on it. ? Also What would the part number be for a 98 4x4 2dr jimmy vin w code. Just want to make sure I have the right one and not the one for a four door in it. And would that make a difference.