yup....since i know you don't like to search much (from when you first joined han) you should have went with the 4-2-1. A 4-1 header was designed to improve top end for the gsr or type r motor, 4-2-1 is low end to mid range power for the ls or in your case the "gs". PM cause i have a dc 4-2-1 header and wouldn't mind trading you for the 4-1