well youve all avoided the actual answer to the questions.
86 gt and st had the pathetic 2se engine with single over head cams pushin out a whopping 93 horse power. 87-89 had the 3sfe. the gt-s had the 3sge for every 4th gen.
the st/gt had drums in the rear and 4 lug pattern, the gt-s has discs all around and 5 lug pattern.
the gt-s came with a factory spoiler for all, the gt had it as a option only.
the gt came as a convertable in starting in 87.
the gt-s has bigger speakers all around and a bigger intake.
the gt-s came with auto climate controol
the gt came with 13" wheels, the gt-s came with 14's
the exhaust has 2 outlets on the gt-s, 1 on the gt/st
the gt came with a smaller stero stock than gt-s
the gt axles arent as strong as the gt-s axles
the gt trany is geared for fuel ecnomy, gt-s for performance
the gt-s has the t-vis intake system (do research on this if you dont know what it it)
the gt had toyota, celica, and gt as emblems on the back, the gts has stickers.
theres more, but i got to get to school now, so i cant spend more time on this.