To outdoor, you have one faulty coil.
Your studder occurs in OD at light throttle application between those road speeds.
This is when the EGR opens and the mixture goes lean, the cylinder that has the faulty coil cannot fire the lean mixture.
As soon as you either down shift or give more throttle the stumble goes away until the next time the same conditions are encountered.
Finding which cylinder is the trick, because it's not a 'hard' fault.
Good luck.