RE: DTC Codes
Code P1510="throttle actuator control limited performance mode". This is essentially a limp mode feature to prevent full throttle conditions in the event of some type of failure.
P2138="Twist grip sensor" voltage correlation error. Both sides of the voltage range when at part throttle should equal 5.0 volts when added together. When they do not, this code is set.
Both can result from the same event in that what may have caused the P2138 can also trigger the P1510. Both can be caused by a poor or momentarily lost connection at the twist grip connector (inside the handlebars).
Since both have been cleared and not returned indicates that they were historical in nature and the cause may have been transient and/or corrected. If they appear again, a trip to your dealer would be strongly recommended to not only diagnose but to capture in history for future reference, if needed.