I havent' read the other posts so I hope I don't repeat info. You may be playing too heavy handed. if you're not comfortable with your chords or you're not sure of what you're doing while improvising you left hand fingering may uncosiously be gripping the neck or fingering the frets harder than needs to be. I've found over the years that my left hand has a much lighter touch now than ever before. you can give sustained notes some shake and vibrato to give the sound some depth. Even chords can be given a nice slow shake but not if you have a white knucked death grib on the neck. i guess the key is to be relaxed and that only comes with time and practice. Hope this helps.