4th generation prelude (92-96) model offers s, si, and vtec
93 is the first year for vtec (in US ???)
s - powered by 2.3L 4cyl 146 hp
si - powered by 2.3L 4 cyl 160 hp
vtec - 2.2L 195 hp (engine code H22A i think)

correct me if i'm wrong =)