At my suggestion, Ford service lined me up with a Focus identical to mine mechanically, and I've been driving it for a week since mine has been in the shop to deal with its ills.
The loaner is great. NO stumbles, stutters, judders, jerks or sudden power cutoff, and it picks the right gear about every time.
For good measure, I'm getting 2-3 mpg better mileage than my own car, driven on the same roads and the same loops thru' town, etc.
Something sure as hell wrong with mine, and I just hope they can find it and fix it. Clutches are reputedly being replaced.