I worked at a dealership in Yakima,in fact,it was one of the biggest dealerships in the state.The service dept was always trying to get us,,the technicians,,,,, to upsell stuff,,aka,belts,hoses,trans flush,,you know,,all the expensive stuff to up the billable hours.One of the things they wanted us to push was fuel system services.GM had their own stuff,,then BG,,,then Wynns,,,different ones depending on the percs that the service manager would get,,you know,,"Kickbacks",,,well all of the technicians would tell the managers as well as the customers,,that these services would help a little,,but not enought to justify spending $189.95,,,so,,,we,,the techs,,decided to create an experiment to see if they really did any good and I volunteered my own truck as the guinea pig.It was a 2002 S-10 extreme with a 4.3v6.I had installed a cold air system and did a little reprogram on the PCM,,anyway,,,we cleaned the entire system according to instructions,,which was a 3 part cleaning.Two cans went into the throttle body and one in the tank and it cleaned up real well,,now,,,here's the interesting part.One month later,we took the throttle body off the intake,we removed the injectors and we took a sample of the fuel from the tank,I usually ran 89 octane.The throttle body was just as gummed up as it was before the cleaning,the injectors were ok,but showing signs of re-clogging and the fuel would seperate from what ever was in it.Oh,,By the way,,,it was top tier fuel purchased from a Chevron station.I guess my point is,,I don't think you stand to gain anything from these services,that you wouldn't normally gain from making sure you run good fuel,,and,,I can guarantee that I will never spend that much money cleaning my fuel system,,knowing that the end results are only going to last,,less than a month.Remember,,this is just my opinion,,if people feel they are doing something good for the vehicle and they can afford services like these,,then by all means,,do what you feel is best