I have a 2000 Chevy Silverado 1500 3dr with the 5.3L V8. I replaced my spark plugs, wires, fuel pump, fuel filter, intake manifold gasket, and lifter valley gasket about a year ago, I used all acdelco plugs and wires. But recently the P0300 was the only code that came up with the normal OBDII screen. and my check engine light will blink. I have found many vacuum leaks and fixed them to no avail. I’ve also tried replacing injectors but no luck. When I use the OEM advanced function on my OBDII(the standard Oriellys one, I work there) reader it gives me a knock sensor code, and many other codes(pics below) any ideas?

 

have you checked fuel pressure?

you've got a lot of exhaust codes which can mess up your mixture. Cats could be failing after 23 years, or you have an exhaust leak, or worn out O2 sensors. Does your tool graph O2 sensor data?