4L80 tuning
I had the same issue with my car with a transgo shift-kit. I made the desired shift-time in the 280ft-lb and less area of 1-2 shift .300 and .000 in all other cells. I also lowered base shift pressure in everything 400ft-lb and lower by about 10%. It still shifts pretty hard, but it's better. Leave Max Line Pressure at the stock setting. Also, make sure if you're running an SD tune that you have Max Line Pressure DTC disabled otherwise it will default to max pressure all the time without a MAF signal.
