I'm receiving the following error codes p300,301,303,305. What are possibl caus

What is your question?

I have replaced Spark Plugs, Spark plug wires, all 6 injectors, coil packs, air intake gasket, throttle position sensor, both exhaust manifolds, all o2 sensors, fuel filter, all cats, valve cover and intake gaskets. I found one fuel injector that had a bad oring and replaced it. I cleaned throttle body. I would like to know if the 1997 toyota has a variable timing solenoid? Any other thoughts on where to go from here?

What makes this problem better or worse?

fixing the one injector o'ring made the problem get better but still throws codes.

How long has your 1997 Toyota Avalon had this problem?

I've been working on the car since November of 2021