The EVP is the EGR Valve Position Sensor.
The EGR is the Exhaust Gas Recirculation Valve.
Look on the back of your throttle body. There should be a big silver valve bolted to the back of it. It should have a white sensor bolted to it that has a black plug connected to it. That white piece is the EVP.
It's very likely that the EVP is out of range or no longer functioning in which case you'd need to get a new one. I really dont know how to check if that is defective so i cant help there.
For the **** of it, you could take the EGR valve off the throttle body (actually its bolted to the EGR spacer next to the throttle body) and clean it out with carb cleaner to make sure it's functioning. Its possible that the EGR is stuck wide open or closed. The EVP tells the computer whether or not the EGR is opening and closing when its supposed to. So technically it could be the EGR or the EVP at fault.
One last thing to check. There should be a vaccum line that goes to the EGR valve. Make sure it's connected, and that its not leaking.