The L298 is a hopelessly antiquated constant-voltage stepper motor driver chip, completely unsuitable for achieving high speeds. Use a modern constant current stepper motor driver chip or module instead. See the pololu web site for a good selection, or do a search on eBay. I think there is or was another chip, the L297, which can be used with the L298 to turn it into a constant current driver, but that's an ugly, complicated and expensive solution compared to using a modern chip or module.
When you switch to a constant current driver, you will also need to increase the supply voltage. It's normal to use these drivers with e.g. a 12V or 24V supply even if the motor voltage at the rated current is only around 3V. The higher the speed you want, the higher the supply voltage you need.
When you switch to a constant current driver, you will also need to increase the supply voltage. It's normal to use these drivers with e.g. a 12V or 24V supply even if the motor voltage at the rated current is only around 3V. The higher the speed you want, the higher the supply voltage you need.