Mr Scout...
Thanks for the suggestion, I think you are on to something. I checked the ground, was able to tighten the screw a little, I also cleaned the plugs on the headsets, it is a lot better. There are a lot of eyelets on the same screw at the bottom of the dash, I might relocate some to spread the load.
It is still a little scratchy, but everyone hears me just fine. Spent some time with center, approach and a tower today, no complaints from them.
I did not have time to try to remove the unit, but may not need to now.
"Never feel sorry for a man who owns an airplane" Charles Morse (Anthony Hopkins) The Edge