Lionel, I'm not having a problem with a high idle speed, the idle is too low. Right now the IAC numbers are around 12 in park and a little higher in drive. From what I have observed, I want to have the largest quantity of the idle air coming by the throttle plate and a minimum admitted through the IAC without the IAC ever going to zero. When the throttle on a TBI engine is closed too much, it will still idle by virtue of the IAC admitting air but that air then has to mix with a dribble if fuel dripping past a closed throttle plate, not the best scenario for getting good vaporization. The more fuel spray that gets by the throttle plates, the better it mixes with the air.
So, the minimum air setting seems to be just fine, the ECM commands a high idle when the engine starts, the engine also goes to the correct speed when in 10K mode. As of now I'm pretty confident that the IAC is working, the ECM is working and the last piece of the puzzle is to use TunerPro to see what the actual values for idle speed are in the PROM. The stock PROM seems to make the engine idle at 600 RPM. The Prom that I'm using now that EagleMark made for me is supposed to have the idle set to 725 but with this PROM, the engine idles at about 550. First chance I get, I'm going to fire up the truck and look at the values. I understand there are many idle speed values for different conditions so, I'm at the beginning of another learning curve. Hopefully, this will be as simple as getting the PROM re-programmed but if the values are correct and the speed is still not right, I don't know where to look next!