I discovered a cheap and easy way to add some back support to the 986 seats.
My '01 986S has standard seats that I found very uncomfortable. Lower back always hurt after a very short while, I could not find a way to adjust it out.
Fiddling around with the seat I discovered the 'pad' on the backrest is attached at the top and bottom, open on the sides. You can see from picture that the sides can be opened with a slight pull.
To increase lower back/lumbar support, I cut a couple of pieces of cardboard to slide down behind the backrest pad. I experimented with various shapes and thicknesses, settled on two pieces of thick cardboard (box for shipping), one taller than the other to make support profile I wanted. Width is a little more narrow than the backrest pad so it slides down into the seatback, and to hide the cardboard.
The cardboard has just the right amount of flexibility and structure. If it wears down or I dont like it for some reason, is extremely easy to remove and replace with something else.
Now my seat is very comfortable with the just right amount of support.
If any of you find your seats lacking lumbar support, hope this helps.