The 1st Gen GS has alot less aftermarket suppport compared to the second. (I have owned both).
Engine-Turbo kits, Exhaust, etc
Suspension- Eibach, Intrax Tanabe springs, Tein, JIC, etc coilovers
Aero-mostly JDM kits- there is a sticky thread at the top of this page
Wheels-endless
I.C.E- whatever your imagination and your small trunk will allow!!
Good luck