1997 Chevy S-10 misfire

Has miss-fire code P300. With Modus, watch cylinder 1 and 4 miss during open loop, as soon as pcm goes in closed loop cyl 2 and 3 are misfiring, the truck does not mis while driving not a steady mis eather replaced both coils, icm, plugs and wires, can and crankl sensor fuel pressure within specs, f p regulator working properly also, vehicle also has 2 new injectors, cyl 2 and 3. Will donate very well when a reply is made that will help us. Thank you, Kirk 480-586-4043