I have searched and read a ton on this site, thats why I joined really is to ask some specific questions. I am aware of the diameter and size differences. Really what I do want to accomplish is a zx with not a huge amount of mods. IE: I don't want to put bigger turbos on any time soon, maybe in some years to come but not soon. I really just wanted some feedback if anyone had some on these pipes is all. I have a Genie catback with genie resonators. I want to take the cats off put test pipes and dp's to the turbos, open everything up. I have a JWT charger already. Would you do an ECU upgrade first or pipes?