Geez, I hate it when something is "broken" then just starts working again with out a real fix - ya know darn well it is still broken but now it works and you can;t fix it... If it had carbs I would tell you stuck floats or dirty needle valves. Have you done a good inspect and clean on the injectors? The only thing I got is perhaps you have a sticing injector and it floods a cylinder with fuel which runs down to the crank case past the rings. You said it runs good - I wonder if that will change over time.
