I used aftermarket plug wires and a lot of them I had to recrimp the ends at the spark plug.
My son's 5.7L in a 1997 GMC pickup started having these type of problems and then the fuel pump falied. When replaced the problems stopped. I would check the pressure with a gage for operating and crimp off the return to check full pump pressure. If you don't have a gage use vise grips and slowly tighten on the return at a rubber hose have some body gun the car and see if it improves.
I would use a spark plug grounded to the frame and check for a good spark.
You also could loosen the exhaust nuts before the catalic converter pull apart appx. 1 inch to check if your converter is plugged.