If I remember right, off line Kartboy has told me that the STi linkage is basically the same as the OEM's but he probably hasn't said anything because he has a vested intrest in saying so. People might think he's just trying to sell more kartboy shifters if he says something. Like he really has to anyway
SM - I replaced Jeff in Lenexa's STi shifter with a Kartboy maybe he wants to sell his old one to you? You can look his e-mail up in the members section.