rough idle/ 558 egr code
 

hey so yeah i have the code 558 on my KOEO test ... had it on the KOER or whatever.... would this cause a rough idle? could it just be the solenoid? i noticed one of the previous owners cut the hose off of the smog pump system after the thing that sits on the passenger side wheel well, as well as the soup can ((vacuum thingamajiggy)in very advance mechanic terms that i do not know:-huh)) what do you guys think???