about the filter here are a few things that you are not considering about the fuel. First you said that the tank was gummed up a little, well new fuel loosens up that gunk and it floats free inside the tank waiting to be sucked up by the clunk, two you are introducing pressurized burned gasses and junk from the exhaust to help pressurize the fuel system. Does this sound like the fuel is really that clean even though it was filtered from the can. Personally I like to use fourmost fuel filter on my planes because they are very small and light and provide backup to my filtered can fuel.