What happens when EG valve on Kia Sportage needs replaced?

it will choke and run like crap eventually what happpens to the EGr valves is they jus plug up ,exhaust gas recirculation valve you should get a check engine light,code po171,po174,or po401,po402. not neccessarily will run rough. sometimes will run fine but thrrough up check engine light for bank 1 to lean,etc..