If you have a question about your own ebike and not the Honda moped in the OP's post, you should start a new post so that other people can try to answer.

That said, at least in California and many other states, 28 MPH is not allowed on a Class 2 ebike. Only a Class 3 ebike can do 28 MPH, but a throttle is not allowed on a Class 3. Class 2 tops out at 20 MPH.