it has the 5.0 liter 305 and is just 4x4, no z71. it is my daily driver and it has about 106k on it. I've had it for about 9 months. about a month ago it started throwing codes. one was the egr for emmissions when it got really cold. the other was something about fuel tank pressure. cleared them and it was fine for a week or two. then the service engine light has been on ever since. Usually it idles at about 1k rpm. but ever since the light came on you start it up and it idles right then when your done driving it and the motor has warmed up it idles right above 500 rpm. Als when it idles wierd if you rev it in park to about 4k rpm and let off it drops down to about 300 rpm and almost dies then goes back to above 500. what could be the problem?