Chevrolet Repair: truck stalls, gmc sonoma, pressure and volume

Question
My friend has an 92 GMC Sonoma V-6 5 speed 4 wheel drive P.U. It runs real good at idle,and at 1/4 of gas pedal pushed down. When he tried to pull up a hill he has to go to a lower gear and only use 1/4 gas pedal. When he give it half pedal it will cut out real bad and not pull. It will even cut out on a level freeway if he gives it more than 1/4 pedal. He has changed plugs. Any idea what he should try next? Thanks for your help.
Gerald

Answer
Without performing some diagnostic tests the first thing I would suspect is the fuel pump is weak and not providing enough uel pressure and volume to the engine and or you may have a restriction in the exhaust such as a plugged catalytic converter.


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