Second, I would seriously visit SpecialtyZ's website and browse through their parts. If you've been gone some 1-2yrs. A lot has changed in terms of upgrades. Regardless of the turbos you choose, the supporting mods below is what you should work towards while replacing turbos Selin Dual Intake (JWT dual intake is a thing of the past) AshSpec 2.5" Intercooler AND Intake pipes (with planar setup) AshSpec Massive intercoolers Larger throttle Bodies. Currently Z1 makes them (with some reported sticking/leak problems) and member Rob'sZ also recently has stuff he's working on. SZ 3" Down Pipes, 3" Test Pipes and 3" exhaust. (proven to be beneficial over 2.5" exhaust. MSP Manifolds
besides having larger injectors, the above would make your 530BB's that you're thinking about run like stockers.