But how did you come to the conclusion that "It appears they're not adjusted for optimum at the factory" Do you have the tools for measuring them yourself?
Trust me, those adjustments were the first steps taken in each of the cases I've dealt with stalling issues (two of my customers). In both cases the adj was not off enough to make a difference (less than half a turn). The adjustment is very sensitive.
They are indeed adj very accurately at the factory, the slight adj I made only compensated for engine break in wear of the rings/valves after a few thousand miles.
Not saying it should not be checked, just don’t assume they are not set correctly at the factory, they are.