Idle stabilizer valve help

[CTDiesel at aol.com]

I'm at a loss with my ISV problem.  The throttle switches check out good and the ISV humms at idle.  The problem is the duty cycle is way to high and the "idle adjust screw" on the side of the throttle body is backed out way too far according to sources.  Does this sound like a vacuum leak then or something else in the system.  Everything has been replaced CIS-E wise except the alt. sensor, throttle switch.  I have read Huw's CIS-E website but still cannot find my problem.

Hope you guys can help
thanks
DJ