a gti is basically just a 1.8 escort but has the rs style skirts on it and they smartened up standard seats by makin them half leather. they put the gti badge on there just to make it sound even sportier to sell more of them. si's were also the exact same 1.8 engine, had spoiler, alloys and front fog lights, but didnt have the bodykit as found on the gti. thats basically it really without goin too far into equipment levels