My car is bone stock, and I get the hesitation and stuttering in the usual 2500- 3000 rpm range. If I floor the pedal, it'll move past that and run fine. A couple of observations:
1. I recently went for a period of time with a driver's side oil control valve that seemed to be working but was throwing a CEL. No stuttering during that period of time, but it has returned after I replaced the OCV.
2. When the car is misbehaving, the engine seems to have very little power, which makes me wonder if the engine controller has the ignition timing at full retard? Or is the OCV in the wrong position for power in that rev range?
3. If I use the steering wheel buttons to initiate a downshift, I see the transmission is usually in a gear that one or two higher than what it seems like it should be for the engine load. For instance, going up a steep hill toward my house, it'll be in 3rd gear, when 2nd is what's really called for not to be lugging (to the point of bogging down) the engine.
Those are my 4-cents worth, that it seems like overly retarded timing, and/or a transmission in too high a gear, probably for mileage purposes. Plus OCV misbehavior.