There is some funny stuff going on with the idle control with these trucks, and I really dont think many have figured much of it out.
If they have, they are staying tight lipped about it..........
Only thing I can suggest is to make minor adjustment and creep up on what you are looking for it to do. This means you may need to make 6 files that are each a little bit different, and see which one works best.
Also, there is a safety concern when setting your idle this way. I can see an accidental "side step" of the brake pedal resulting in an accident. But for you OBS guys I dont think there is any other option when trying to duplicate an "automatic idle".
Just out of curiosity, did you remember to convert to Fahrenheit?