I agree! All I use is 15% and it works just fine. If you installed the fuel line that came with the tank, that could possibly have holes in it. The stock fuel tank lines are usually thinner and can get holes in them very quickly. Or it just could be that the carb isn't tuned in yet and you need to set your low speed needle again. Do you have an inline filter between the tank and the carb? Sometimes they can leak and lean out the engine.