1991 gmc 1500 z-71 having problems keeping it running?

[jamies_princess_28]

problem's running I have a 1991 gmc 1500 z-71///// 4.3 engine 5 speed 4wd when you hit the throttle half or more it will not run but if you let up it will run ware do you find Schroeder valves.i replaced the fuel filter and already and the fuel pump is not even a year old any one know or any help thank you

 

[DonE]

Check the plastic vacuum line from the MAP sensor to the throttle body,it may need repair.