2002 E825 jerks and shutters while driving

My gem has around 9,500 miles on it and for the last 2 years it has shuttered and sputtered while driving. The controller has been adjusted to allow it to run 34 miles an hour. It seems the faster you go the less it does it. it is worse at 15 to 24 miles an hour.
Any suggestions?

Motor brushes are sticking. Need to be serviced.


Who/where modded/reprogrammed your controller for you?