i can surply both for you
the fuel system cleaner will clean all the fuel system ,but wont unblock blocked fuel filters ,so i would recommend u change your fuel filter first then add a whole bottle of cleaner in the fuel tank,dosnt really matter how much is in there ,anywhere around 1/4 tank is fine ,just put itin the tank and just drive it,and let it do its work
really dose help to stop build up on the valves and pistons etc