Silverado p0300 code

[danny]

Have a 05 silverado had the 5.3 in it has a p0300 code mupital random cylinder misfire code can clear code truck runs good unit reach about 40 mph check engine light flash same code runs horrible hhave put new injectors new coils new plugs&wires iintake gaskets new fuel pump 02 sensors have cchecked all grounds no vaccum leaks that can find any suggestions would be greatly appreciated lost on what could be the issue

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[Richard Kirshy]

Just a thought …
Possibly:
Faulty fuel pressure regulator.
Faulty cam / crank sensor.
Faulty O2 sensor(s)
Partially clogged cat

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