Sputtering under harsh acceleration

[jacob buza]

I have a 91 c1500 I just plugged a hold in the tank and put a new fuel sending unit and pump in it and now for some reason it seems to fall flat on its face when I put my foot past 1/2 to 3/4 and will not accelerate almost like its running out of gas but its got 3/4 of a tank. I ease off and its fine it did this a couple times when it got super cold (10 to below 0) but went away when the engine warmed up, well I didnt get it to operating tempature but its 50 degrees today so I dont know if theres something wrong with the brand new pump, dead spot in the throttle or just needs a tune up that bad. It is a sh*t box and it is a 4.3 with a 5 speed manual feel free to ask questions and I will be updating tomorrow when I get it up to normal tempatures

[jacob buza]

Also it does the same thing when I just rev the engine in neutral normally it'll just rev up no problem at all