If the element is not stock you don't know what you really have for audio response.
To begin, use the Menu button, turn to #21.
Use head phones in the front panel jack and turn on the audio monitor using FUNC and PWR BUTTON.
See what you can get from the radio TX Eq.
Then set mic gain to just hit ALC a bit on the signal meter using MIC button and adjust with the Multi/Chan control on the right side of the front panel, for that level.
If you still don't get what you want, it's time to replace the element or do some circuit work on the mike.
Menu 22 is TX band width. Be sure its 2.8 or 3000 hz for the widest audio.
Or get another mike like a Beringer XM8500 or equivalent for good audio.
Good luck.