My 2012 Prius has 15,000 miles. I just took it in to the dealer for the annual State inspection. Just like last year, they told me there is "carbon build up" and I need the "EFI service" and "throttle service." Which luckily is on sale for "only" $199. Do I really need this, or is it just a rip off? Last year they also told me I needed new air filters, at an insane price. Thanks.
I went 12 years and 288k miles without ever doing an EFI or throttle body service in my 2004 Prius. Dealer service writers are notorious for doing "upsales" for services that are not needed. JeffD
Under normal conditions it is not necessary, otherwise Toyota would have listed it in your service booklet. "EFI service" = Pour one $10 bottle of Techron into the gas tank. - 1 minute. "throttle service" = Remove air filter, stuff a rag below the throttle plate, spray 1/4 of a $10 can of throttle body cleaner and rub a little, remove rag and reinstall air filter. - 5 minutes. And if they did nothing at all, it wouldn't make a difference.
Use a quality gas, the injectors should be fine. Throttle body: maybe in another 35K miles, clean it yourself. See @NutzAboutBolts video on throttle body cleaning, pinned in the 3rd gen maintenance sub-forum. The Prime is another car, but the principles are the same.