How did you measure speed?
I measured by HOLUX brand GPS on two different 1000W drives.
Anyway max speed here is so subjective depends on so many factors like wind, weight of rider, tires,etc.,etc.
But the fact ebike drive on JUST 36V can reach 28mph on its own/no pedalling/ is remarkable!!
You see we don 't know what software is loaded on your motor controller, dash 1, or dash 2.
You say it was 2010 ,only 5 years ago , you might have dash 3 software which allows for it.
Again, how did you measure speed?