More than likely R134a. It should be listed somewhere on the A/C unit.
According to the Auto Car website, the most popular Honda Civic is the Honda Civic Type R Mugen. The Mugen is a sporty type of Honda Civic with tail wings above the trunk of the vehicle.
Freon' is a brand name for 'refrigerant', the type of refrigerant used on early 1990 Honda Civics was R-12. Now a license is required for someone to properly charge the system so many owners have switched to R-134a.
No different dashboards and cluster wiring are involved. Honda also did not make an SI in 1991 and the car model and type is nearly completely different.
R134a
Honda civic is faster but better?
The 2006 Honda Civic has single overhead cam (SOHC).
The 2004 Honda Civic has single overhead cam (SOHC).
The 2003 Honda Civic has single overhead cam (SOHC).
The 2011 Honda Civic has single overhead cam (SOHC).
The 2009 Honda Civic has single overhead cam (SOHC).
The 2012 Honda Civic has single overhead cam (SOHC).
The 2013 Honda Civic has single overhead cam (SOHC).