K20, but definitely a very under tuned version compared to the type R's K20 :P so, go hard or go home, type R or just forget about it. U'd want a TSX over a RSX type S, but if you already own one and you realise you've made a tremendous mistake because you thought a type S would be fast and wanted to do up a replica cheap version of the type R then it's ok. Don't cry, u've failed but it's not the end of the world or anything.