When you hear a P25 comm, press Hold/Man, then press the 9 key. The talkgoup has to have a signal in order for you to adjust the sound quality. Once you dial in the best sound, thenn press "E" to save the setting.
I don't remember if the 250 has the autotune feature, but the BC296D/BC796D has autotune when you do the above and then press Priority/Transfer button. Once it autotunes, press "E" to save the settings.