gmc 1998 sierra idle problem

Hi I have a 1998 sierra with a vortec injection but these last days I have notice the when I want to accelerate it decreases the speed and it turns off when I want to idle more.
I have changed the fuel pump but it does the same, I took it to an Autozone and they didin't find and error code with a OBDII scanner,

can Anybody please help,

Good morning,
can somebody help,

Regards.