As far as I know it would be off by 1 mph or 2. Don't believe the software accounts for tire size change.
The bigger question is if it would impact brake/suspension/drivetrain warranty at all?
Besides the added mileage from them, I just love 1 pedal driving. The smooth stops they make, the decreased wear on brake shoes, but what I love the most is how they help set up a great winding country road curve. Let off the gas go pedal setting up the turn and let the regen brakes get you to...