I finally managed, I repaired the footwell actuator in my 1992 Porsche 928GTS.

It was  a bitch. Not a quick and easy job.  Took met the better part of two days to do all the work around getting at the actuator and 15mins to do the actuator itself and test both center console and footwell flap actuator.

This is a step by step.

  1. remove the power strap at the battery as you don't want any shortcuts causing problems
  2. remove both side covers from the center console (left is two screws, right side has four). Remove the lower right screw of the gas pedal protection plate to get it out easier.
  3. to start with removing the knee protection panel, remove the 10mm nut under the dash, above your left knee.
  4. there's one more nut at the air duct in the far left. Remove the rubber-plastic cover by pushing in the tabs and remove it. This gives access to the spiral air tube. Move it aside and look for the bolt holding the protection panel to the upper dash. 10mm. Remove the nut and washer, don't loose it....
  5. remove both 13mm bolts holding the panel to the center console frame.
  6. remove the hex-key bolt just below the steering tube.
  7. remove the panel. Mind that there is a distance pipe located on the far left bolt.
  8. remove the screw (left) under the dash, holding the center console to the upper part
  9. same on the other (right) side
  10. loosen the two screws that hold the center console in place at the rear of the console.
  11. pry out the center-vent air screen. Carefully, don't break it and don't loose the little plastic pieces that go in the pin-holes
  12. remove both 8mm bolts that go up in the upper dash
  13. add some thick paper between rear of the center console and the arm rest box, to avoid damaging. Tape it in place.
  14. remove your radio
  15. does your dash move to the rear?
  16. if so, you're lucky. Go to to #23
  17. remove the ecu cover and the upper one just above (small)
  18. remove the glove box. Some screws.
  19. remove two 10mm nuts at the rear of the box. It all comes down now. Pop off the shock damper.
  20. disconnect cables to avoid breaking things
  21. remove the latch that catches the glove box (2 screws and washers)
  22. find a long bent 8mm ring wrench that fits the 8mm bolt far below where the latch used to sit. Hard to see. It needs to come out. It is frustrating and time consuming. I tried ratchets, sockets, open wrenches, flexible wrenches etc etc. The ring wrench was the only one. A flat one won't do it. It needs to be a S style .
  23. after that the dash slides backward a little. You can choose to remove all cables or just slide it back to make room.  The instrument console sits in its way a little but you can leave it in place by turning the console a little to the drive side (so not straight backwards)
  24. form there onwards it is simple.  Replace the membrane by popping off the box lid. Leave the assembly fixed on the air box.
  25. Assembling is in reverse order.

Picture borrowed from Rennlist. I think from Nicole Mossinger

No, it is virtually impossible to access it from the airbag cover. I couldn't open it. Dunno why, it's stuck on the hinges, maybe never intended to be folded towards the window.