A car witha street ported engine with over dirve pulley and upgraded ECU has a idel that hunts/ stutters from 750 to 1700.



i'm thinking intake leak



or



TPS



it goes away when i turn on the lights the hunting that is and idels sorta high in the 900 to 1100.

 

When you turn on the lights you will rely on the electrical load circuit a little... or whatever the hell its called. I know lots of people that have a crappy idle until they turn on at least the parking lights..



Look at your throttle cable... If there's a little play in it try to tighten it. It fixed my low, stumbly idle...



But also, if I remember correctly, a ported motor will idle a little rough.



You could also have a vacuum leak, crappy plugs, and a number of other things...