If I were on a tighter budget than I am I would run the 2.5" cast manifold with the J-pipe just you. In fact, I honestly wonder if I went the right direction. You will make quite a bit of horsepower before this setup will be holding you back enough to require a change. Making clifford or langdon shorties into a single turbo header will be a lot more complex and not a whole lot faster.
"The first rule of overkill: You can never have too much overkill." "Overkill is underrated."
