How does carbon accumulation inside the exhaust pipe and silencer of a two-stroke small engine affect engine performance?

1. It restricts exhaust gas flow, increasing backpressure to levels that prevent fresh fuel charge from entering, causing power loss and overheating.
2. It cleans the exhaust emissions by acting as an organic carbon filter.
3. It increases engine top speed by accelerating exhaust gas exit velocities.
4. It causes the engine to run lean because the carbon absorbs fuel vapours.