Stalling Under Acceleration

[1995HB4X4]

About six months ago i noticed that my truck was slightly hesitating when i accelerated from a stop. I didn't think much of it then but now it stalls out completely for about five to ten seconds and then goes making it pretty much undriveable. Once the truck gets above 2000 rpms it is fine. I have been searching on this topic for months and have been reading the fsm and haven't found the solution. It will only stall under load and it is much worse when it's at operating temp.

Here's a list of parts that have replaced since the issue occurred:
Cap and Rotor
Plugs and Plug Wires
O2 Sensor
Fuel Pressure regulator (Adjustable aftermarket one)
Fuel Pump (Walbro 255)

My first thought was fuel starvation so i tested the fuel pressure at idle and actually ended up with around 60 psi rather that the stock 33 psi at idle. I bought an adjustable on with a built in gauge and set it to about 40 psi and it still stalled just as bad. I then noticed that my fuel pump was whining a lot louder that it used to so i replaced it with a walbro and i still have this same issue. I am not running any emissions on it and i had the problem before i removed the emissions. Does anyone have any ideas? All of the other posts i have seen on this issue never have an answer to what the problem was.

[S13_RB25]

Did you gap the plugs?? Also try checking for any vacuum leaks.

[1995HB4X4]

The Plugs came gapped to stock spec so i wouldn't think that they would be a problem but just in case what do you recommend for gap size. I also don't think that their is a vacuum leak because i am only running two (FPR and Brake Booster) but i will check again.

[1995HB4X4]

Just unplugged my oxygen sensor and went for a drive and it was much better. It doesn't stall anymore but still hesitates under 2000 rpm. I replaced the oxygen sensor a little over a year ago so i don't think the oxygen senor is the actual problem it just makes it somewhat drivable now. Any ideas on what would cause this?

[S13_RB25]

I would still say check for vacuum leaks and the spec for the plug gap is any where from .039-.043. But gap them as close as you can to .039 so you can get the max wear/life out of them.

[1995HB4X4]

No vacuum leaks. The plugs were gapped at .034 so i regapped them to .044 (stock spec) and it made a slight improvement but it still hesitates. I am thinking of replacing the oxygen sensor and see what that does even though i replaced it about a year ago.

[S13_RB25]

.044 is out of spec for a ka. Also what about he fuel filter?? When was the last time that was replaced?

[1995HB4X4]

The fuel filter is only about a year old. I found several places that said stock gap is .044 but i may try a little smaller and see if anything happens. I am starting to think it's an injector problem because i am getting terrible gas mileage like 10-15 mpg and when i pulled out my spark plugs they seemed wet even though i let it sit for probably 45 minutes before i pulled them.

[S13_RB25]

Um well when its running, at idle, try unplugging a fuel injector one at a time. See if that makes the motor run any different and if so that injector is your problem.

[1995HB4X4]

I threw in another set of injectors from a junk yard and put some fuel injector cleaner in with the gas and i swapped another CAS i had laying around in and it runs smoother (especially at idle) but it still lacks some serious low end but it it won't stall anymore even with the oxygen sensor plugged in. I am considering replacing my oxygen sensor again because when my fpr went i was running extremely rich and i think that may have ruined it.