Car is straining at 40mph or whenever gas isn't being pressed hard enough.

What is your question?

The car is running very weak. It feels like if I don't keep my foot on the gas,it will immediately slow down. At first I thought it might be gear,but no since it can get to 60mph,but feels like it's straining. The check engine light went on and has been on for a while now. At first I thought it was fluids but all checked out fine and no leaks. I just failed inspection at motor vehicles and they took the time to show me the codes that showed up. They were P0404 and P0405 which is telling me (from this site) the EGR Valve Position Sensor or Valve may be to blame. I'm wondering if I should just replace both the sensor and the valve? Would this be an easy enough job to do?