i opened the valve while it was running and it kept running, no fuel came out, there was no hose anyways, they're might have been a few drops that came out as i was taking it off

If the engine kept running and no fuel came out,the hose is plugged with debris,it would be wise to clean or replace it.

Another test along the same lines would be to open the bleed valve on the fuel filter with the engine running and see if fuel comes out or stalling occurs,it makes a bigger mess then though.

how would i clean the line? and how do i bleed the filter?

Going down different road: does the truck have a catalytic converter?
plugged cat = power block + exponentially increased blow by = fuel in the oil = high oil reading but low oil pressure

if this is possible, DO NOT RUN, you will ruin crank bearings / engine real quick (been there, done that)

not sure if it has cat. makes sense it being a fuel problem as it stalls going faster i.e. needing more fuel and going up steep hills.

---AutoMerged DoublePost---

there is a black hose connected to the side of the t valve, its connected to nothing...should it be connected to something?

Have a run through this Lift Pumps & OPS operation and troubleshooting 1st thing you can do is put in a new fuel filter, a partially blocked filter even on a recently changed one can cause a lack of power issue as one can get a bad load of fuel at any time.

---AutoMerged DoublePost---

94 Tahoe most probaly has a cat, look at your VIN 8th digit S is a EGR vehicle and has a cat, F digit in VIN is non EGR and should not have a cat but may depending which market the vehicle was to be sold in emission check state will most probaly have a cat even with the F in the VIN, easy enough to find out look under the vehicle see if it has (2) muffler looking things in the exhaust one will be the cat, the one just after the turbo downpipe is the cat.

i read that link. i can't do the test at 70mph because i can't even get past 55mph without stalling. is there an additive i could put in to unclog anything? most of the things on that link are way over my head and i can't grasp what your saying. what can i open up to look for clogs? or something along those lines

1st thing (IMHO) is see if it has a catalytic converter
if it does, disconnect / temporarily remove and see if makes differnce
as I noted in prior post, look for raising oil level (blowby = raw fuel added to engine oil)
plugged cat killed my prior engine . FWIW, crappy installation by shop messed up turbo dump, so was dumping too much fuel... AK (I summer in AK) fix was removing cat (which was plugged so bad, would not let drop of water through after an hour when stood on end), flushing with Muriatic acid (pool acid)

No additive to clean up this kind of problem; and you don't have to run to 70 mph, a loss of fuel pressure from the lift pump will show up at lower speeds, and limits power you can attain, have you changed the fuel filter yet?

Plugged Cat (Catalytic converter) is a possibility but not common, what is 8th digit of your VIN, you need to read what I linked you to and try to get as much from it as you can then post back what exactly it is that you do not understand. More info here Acronyms "What you talking about" also some Diesel basics specific to the 6.5 6.5 Diesel Technical Library and a visual of where parts are and what they are called Part Locations

If I was there I could show you but I can't so you have to be as specific as you can so we can assist you otherwise you wind up spending money you may not have to spend.

Assuming you are still stock exhausted, a 4" turbo back system should be your first upgrade and will eliminate any cat issues forever.

the 8th digit is an s, so it has a cat, but the previous owner put a new exhaust in or muffler. i don't have money at the moment to get a new fuel filter or the gauge to test the lp. lets say i did test the lift pump and i do need to unclog the lines. how exactly do i unclog the lines or filters, i couldn't find any info on doing that. also if i could get a link on installing a new fuel filter