Possible airflow issue, trying to verify AI advice

2015 Prius, 350k miles. A few months ago, the hose for the engine air filter was improperly connected for about a month after a repair job. Car had been running great for a while, then one morning started running really rough, and threw off a check engine light, P0303, misfires on cylinder 3.

Took it to the dealership and got an oil change. Car was then running a lot more smoothly, and a kind of grinding or chittering sound I'd asked about a few weeks ago went away. (Think I'm going to switch to a 7,500 mile oil change schedule.) But they refused to give me any info on the engine code without paying a $99 diagnostic fee.

So I ran the car to Auto Zone and got the error checked, as I said above, two P0303 errors. Started checking with google AI to try and figure out likely problems. Explained how after oil change, things were much smoother. Was told that the oil change *might* have solved the problem, and if so, the check engine light would turn itself off after a couple of days. (It did.)

But it also said there was a good chance the airflow sensor might need cleaning, especially after that loose hose for a month, a little while back. It also said very common with the age of the car to develop heavy carbon build-up on the intake manifold or something like that. Said there was a three step process involved in cleaning, and that quite possibly, the first, easiest step might be enough to clear the problem. (Supposedly something about Prius engine design means it's most often the 3rd cylinder.)

Anyway, I was told the airflow sensor was easy enough to clean, and the four videos I have watched back that up. The air intake thingy is a more involved process, and is going to have to wait a month or so until my handyman heals from a hernia surgery, but I'm told that shouldn't be a problem, and that just the sensor cleaning might fix the problem.

For the sensor, I got the proper CNC or whatever it was airflow cleaner, and that ought to be a simple project for today.

Oh, yesterday, rough idle at startup, check engine light came back on, which is why I bought the cleaner for today.

Does all this sound fairly reasonable, and not completely insane?