Rough start and stutters when giving gas

hey, I have a 2010 Toyota Prius w/ over 300k miles on it (yes, a lot). My car was reading codes for a EGR valve and misfires from the cylinders. It got to the point where the engine was shaking unless I gave it more gas

So I ordered and new EGR, spark plugs, new ignition coils and gave it a new synthetic oil change. Now still shaking when engine on and say issue when I give it gas, it shakes unless I

Had the mechanic pull the codes after the work and it came back as:
P0300-P0303

No other codes

Cylinder 1-3 misfiring

My mechanic is confused and blaming it on the engine. Saying it might be going bad

I was reading and watching some videos on similar issue and it pointing to the fuel injectors. I’ve used the bottles and poured them into my gas tank but still same issue

What do you guys think? I was thinking a Fuel system cleaning might work but willing to take any recommendations. Thanks in advanced