Reduce the RPM limit. The best way to know where you should set it is to collect a data file while running flat out to record rpms at your current top speed. If that number is say 4000 then you can set a limit of 3000 and know you will get a 25% reduction in top speed. Remember to
SET your changes before closing the program.
The Alltrax toolkit software and user manual is here >
https://alltraxinc.com/alltrax-tool-kit/