Rich doesn't blow engines, it just makes them slow.

"Lean is Mean"

If you run too lean, EGT will climb, and you will get knock. The ECU will try to add fuel, and retatd spark in response to the knock sensor, and O2 sensor readings. Once the ECU runs out of range on its fuel map it will set a check engine light for lean condition, or low O2 sensor voltage.

John C.