1999 suburban dies out after 20 miles

On my way to Wisconsin the truck started to shutter the fell on its face. The check engine light did not come on. We pulled over and let the truck sit for about 10 minutes then it ran like a new truck again. After about 15-21 miles it would shutter loose rpms especially uphill and go to 1000 rpm and idle itself along the edge of the interstate. I have already replaced the fuel pump and fuel filter. I replaced the cap and rotor and the truck ran good for about 2 hours then it started again. On the way home I stopped in Rockford when the check engine light came on. It said low voltage to left back O2 sensor bought and replaced it. Still no help. By the time we got home over 7 1/2 hours later the truck was making it 7 miles before it had to take a rest to go again. Truck is a 5.7L. The old cap had wear in it on the 8 contacts. The new cap was already getting wear on it by the time we got home. Could the distributor be the problem??? I have new plugs, coil, cap, ignition module and plug wires to install. ON Christmas day!! DOes anyone have any other ideas?

make sure the gas cap is working properly. If you drive it and it stalls, jump out and undo the cap to see if you hear vacume/suction sound. if so, replace the cap.
You said you did the pump and filter, check for running fuel pressure. this is a in line fuel guage taped into the fuel systems line of pressure.
drive the vehical to see if you loose fuel pressure after a short time. I did 5 fuel pumps in my gmc before I got a good one. dont by aftermarket, get a gm pump. and . you could have stired up a load of crap when changing pumps, re-check the filter. pull it off and blow through it.'

post what you find.

Can you feel play in the dist if you try to move the rotor side to side? There should not be any wear in a new cap and rotor.

//2000CAYukon

new fuel filter and no pressure at the gas cap. Now it is showing the p0151 O2 sensor code. You can smell raw gas with the front windows down. If you push the excellerator to the floor it jugs and back fires in the catalytic convertors it sounds like. I do thank you for your suggestions. I will check to see if there is any play in the distributor next.

mine did this as the fuelpump was only pumping 5lbs to 25lbs and supposed to be 40lbs constant pessure. also the backfiring is not good for the sensors my '02 silverado would quit after about twenty minutes driving time and it turned out to be the crankshaft position sensor. the 8.1 vortec and 5.3l have alot of crankshaft sensor problems.major symptom it quits as it goes down the road, cools off cranks back up for a short time dies again.