Just purchased an 85 RX-7 GSL and decided to change the fluids as the car was sitting for a while. After doing the manual transmission fluid we stumbled into this mysterious rubber plug. It is located forward of the manual trans plug and right behind, what I believe is the oil pan. It looks like a plug, it’s a very soft flexible rubber and it feels glued into place. We have no idea what is behind it. We tried to find it in the manual but could find nothing of such a drain. The rubber plug is circled in red in the attached images and what we think might be the fill plug as well.

Couple other side questions…
We think we found the manual transmission plug torque, but in the technical data it was very low (4.3-5.8 ft-lbs). Afraid this was too low, we used the torque specified for the 2nd gen RX-7 (I think around 20 ft-lbs). The manual trans drain plug was also magnetic. Was this a standard plug or an upgraded plug in time?

As a side not please correct me if anything is wrong! And hopefully everything is a-okay with the post! Thanks for your time!

 

it's an inspection plug for the trans.
it is like a Circular Lipped grommet type stick in plug.

 

Thank you!