ford explorer missfiring ?

I have a 1998 explorer sport 4L overhead valves W/ ac just installed power steering pump and now when she idles it is bucking and skipping until I drive and get to over 2000 rpms and then she seems to smooth out. the eng serv lite is on so I put it on a code reader. it said the egr valve regestered too high a gas flow. does anyone have an idea for a fix? thank you, Rick.