SITL Lockstep Frequency

I’ve noticed that using lockstep in simulazion (SITL) with Gazebo the simulation runs at 250Hz mostly, even if i raise the gazebo world frequency to 1000 Hz, and also setting the IMU_GYRO_RATEMAX higher then the default value.
Someone knows how i can keep Lockstep and run the simulation at higher frequency? is there any parameter to be set?