I wanted to let you know that the 20 mph maximum speed on your bike is a result of Federal Law regarding electric bicycles. By law, any electric bike that gives you assist over 20 mph is in violation of this law and is not actually legal to ride on the street. Since we want our riders to have bikes that are fully legal to ride, we have set this 20 mph limit.
Here are the relevant laws:
However, your EVELO does have an off-road-only mode, which will allow a higher speed. Any use of this mode on the street would be at your own risk.
Take a look at the manual for your control panel here: http://www.evelo.com/displaymanual.pdf
On page 7 and 8, in sections 5.1 and 5.2.2, you can find instructions for increasing the maximum speed.
I hope that you find this information helpful.