I had a clogged return (not the line, the carb itself) but it was like 3 yrs ago, so its possible i'm remembering wrong...
anyways...
If i remember correctly, it caused a bog/hesitation around half throttle, or when I feathered it.
made me think I had a bad plug, like it was skipping.
ran just fine when throttle was pegged. But then i'd get that skipping when I slowed down and tried to give it just a little bit of throttle.
sticking a very small wire in cleared it up.