I have been able to go up to 25MPH and have not hit a wall at 20MPH. However, the power will normally stop at around 18MPH and the remaining 6MPH is through peddling. The code 3772 does not come up on the Trek BionX unit.
Someone emailed me on how to get more assist over 17MPH. The only way around this is to change code 008 to gives you extra assist at 17MPH. There would be trade off you would have to peddle harder to get to 17MPH.