Cleaning the fuel injection system is one service that I do not totally object too. There is some technical reasoning to it, mind you I say some. GM will go for it as long as it is their process, they do not approve of other methods (but they are all pretty much the same). The main gripe(s) I have is that the fuel itself should be doing the cleaning and the cost of said service.
Cleaning the throttle body is a no brainer, yes it should be done and only takes minutes to do,at most a .3 charge,perhaps .5 on a difficult to reach car.