Octane plug - LeMans Import 1988

[autominus]

Hi,
I am owner of my Pontiac Lemans Import 1.6L (year: 1988). This car was imported to Europe and I can't find the octane plug for selecting the optimal fuel grades.

Example of an octane plug picture:

Where is hidden octane plug?

Thank you in advance for your help.

 

[melsg5]

Since this car was a Daewoo, I found this discussion on a Dawoo site referring to the plug being under the seats/near the ECM.

http://daewootech.com/forum/viewtopic3874-2.html?f=1&t=13950&start=0