Do you have a cam in it? If not then I don't see why you would need to mess w/ the cable. That just seems strange to me. I would think the idle speed would be controlled by the PCM via electronics, not by having the cable hold the TB butterfly open a bit more.
I'm no tuning/electronics genious but I find it odd that once it starts getting up to temp it gets a bad idle. Almost makes me think a sensor is getting into closed loop and loses its mind somewhere or something in the PCM isn't quite right.
