Its an art. I like to set up using oem specs and dial from there. Then there is dealing with carb ice,high humidity and below 65 degrees, i have seen cabs frost up.
Beleive it or not Frank, your words give me encouragement.
One extra challenge with this 2150 is the factory specs aren't consistant. There was a change in 1985 factory service bulletin which is what I've been using.
The choke pull-off that died was a positive close type (spring on the outside) but the replacement is a modulated type.
I don't have experience with the modulated one, and I'm not 100% sure its correct, but I think it is. Not sure that this should effect the mid throttle. My thinking is that by mid throttle the choke is being pulled open by the unloader through the fast idle link.