The reason those bottles of dump in don't work that well is because all they do is trap the gunk and grime it removes from the fuel system in the injector screens. If you have never seen one those things are sooooo small. If you really want to clean your fuel system you either have to remove the injectors and clean them after you flush the system or use an actual machine. The reason machines work so well is because they cycle cleaner in and out of the fuel system actually removing buildup.