I've been racking my brain and looking around though pages of dyno sheets on here, club na-t and supraforums. I'm shooting for 500 on the ground at the absolute max on pump gas on a na-t with a tt hg. A broad power band with minimal spool is key for me. I'm in between the T4 Gt35R, a 61mm, a 67mm, or a Holset HX40. Anyone have an experience with these set ups? Any constructive info is greatly appreciated. Thanks.