I’m sure they actually clean the throttle body and run a good quality cleaner through the fuel injectors. But, it is overpriced and typically unnecessary. I have a 21 year old Supra that has NEVER had the injectors cleaned, and it runs good with 250,000 miles on it. I have cleaned the throttle body, though, but that was after almost 80,000 miles the first time. On this car, I have to remove the throttle body to change the platinum spark plugs, so I went ahead and cleaned it.