read the KR stickey. the eaton puts in alot of hot air and adding a smaller pulley just increases the hot air. with the stock exhaust the hot air can not escape the engine thus causeing knock. when it knocks the computer pulls timing. pulled timing equals SLOWER car. there have been many of stories of pullied gtps losing to stock pullied gtps. ask bio about that one also ask bluegtp about the motors the zzp pcm blew..