i have messed with the motor timing settings with the ezrun 35amp system and motor that i had in a on-road car.
the higher the timing, the slightly higher top speed i seemed to have. however, the higher the timing the greater the drain on the batteries.
i run all my ESC's at zero timing. the gains of increased motor timing just dont seem to be worth the strain on the motor/battery IMO.

but it wont hurt anything to adjust the motor timing setting and test the truck on different settings. you may find you like increased or decreased motor timing. its more of a preference thing. the adjustments dont make a huge difference in power/speed tho.

think of it like adjusting the timing in a real car motor(older models with a rotor)
when you advance the timing on a car, you increase the HP and torque at a lower RPM value. there is no real increase in HP or torque, it just changes the curve to bring up those values at a lower RPM.
sorta the same with the motor timing on the ESC. kinda changes the HP curve. but like on a car, changing it can decrease gas milage(or runtime.)