Low power under load

2001 CHEVROLET LUMINA V6- 3400 64,000 miles. Car has low power giong up hills. If you press gas pedel to floor car will down shift and Check engin flashes. I plan to get code read Saturday.

No ccodes found. Spark plugs replaced air filter and fuel filter replaced. Improved power.

If you didn’t replace the spark plug wires at the same time as the plugs, you should consider doing that too. Those wires are in a very high heat environment and can easily be compromised, resulting in more misfire problems. A flashing check engine light means the engine is misfiring, so I’m very surprised you got no codes.