I want to build my own exhaust from parts that I am going to get from burns stainless. My question is this - I am NA right now but plan to go FI in the next year (after my move). I want to put my exhaust on before then however. Is there a compromise? I can handle loosing a small amount of low end on a bigger pipe, but what would you recommend that would be enough for FI? 2.5"? TIA.