1996 GMC Sierra 1500 / why does it misfire when accelerated!

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Will crank and idle fine but as soon as you accelerate engine misfires. When I get moving it runs fine from about 30 to 70 mph. I have changed the following parts without improvement . Fuel pump, filter (air and fuel), injector mechanism in manifold, throttle sensor, oxygen sensor, spark plugs and wires, distributor cap, rotor cap. Also replaced fuel with premium and added Lucas Cleaner and cleaned the throttle body. Twice I have grounded battery cables to reset system which does turn turn SES light off momentarily. Engine Soon light still on.