How does a clogged or dirty air filter element affect the air-fuel mixture and overall engine operation?

1. It restricts air intake flow, causing a rich mixture (high fuel ratio), poor fuel economy, loss of power, and black smoke.
2. It allows too much air to enter the engine, causing a lean mixture and overheating.
3. It increases the engine idle speed automatically, causing the clutch to drag.
4. It forces the engine to run without lubricating oil, leading to immediate seizure.