Its not common for the fuel pump to break down.
I think There are dirts in the path, but to be safe change the spark plugs and use STB to clean the injectors (do not remove the injectors unless you are changing them) That's what would I do
Also clean the air filter cuz the dust cuses the engine to use more power to get the air in which mean more fuel.
I had similar issue but once I replaced the plugs and air filter cuz it was to old to clean, everything turned better.
Hope I helped
I've braking issue with my ls400 so I parked it far at my grandfather place till the parts arrive, tomorrow i'll go to clean it and check the fuel electronic system for you.