2005 Toyota Corolla Engine Revving

Hi!

I own a 2005 Toyota Corolla that I bought new. I have had hardly any problems with it until a few months ago. Our check engine light came on, and after getting the codes pulled off, we found it was simply an O2 sensor. A few days later (after putting some fuel injection cleaner into the tank) our engine started to idle roughly. In park (or when stopped with the brakes) it would rev itself and then go back down, sometimes quickly. A few days ago, it went into limp mode, where we could not rev above 10 miles an hour. (Check engine light came back on) We turned it off, and then turned it back on, and it was working normally again. We brought it to a shop where they hooked it up to a computer and did diagnostics, and found that it was the throttle body computer (I believe that was what it was called). We paid for it to be replaced, along with the O2 sensor yesterday.

My question is, it is still revving, though a little bit less. The mechanic said it might idle "high" as the car got used to the new computer, but I am wondering if idling high is the same thing as revving up and down.

Any ideas as to what could be going on? Is it the Idle Air Control? I know less than nothing about cars, so any ideas are appreciated.

Thanks!