Hello I have a 1998 Chevy k1500 5.7, I recently put in a new 5.7 crate engine .40 over. Swapped all the old parts over and got it running and timed. Ever since we got it timed correctly it almost feels like a misfire past about 30% throttle. Very low in power and has a very rough idle almost dying sometimes. I’ve checked spark, air and fuel. Only problem is fuel pressure is a little below 60 during idle and pre ignition. There are no codes at all. Voltage to fuel pump relay is as it should be. I’ve replaced spider injection unit, fuel pump, cap, rotor, wires, plugs, maf sensor, map sensor, fuel pump relay. Kinda stuck at this point been wanting to take it to a dealership but don’t want to spend an arm and a leg for diagnosis. Any suggestions? Also have checked grounds and wires around injection unit. Thanks!