1. Dual (Selin) Intake 2. ECU 3. Cat Back Exhaust 4. Down Pipes 5. Test Pipes or High Flow Cats 6. Inter-coolers (you may want to hold on this one) 7. Boost controller 8. Injectors eventually your injectors will fail count on going new style and 555. With a little extra $$$$ just go 300* fuel rail w/ 740's 9. Full breather mods. (2.5" intake/IC piping and IC's) 10. Once you have all those mods you will be like I might as well replace turbos think Sport 550s and MS Manifolds
It all comes down to planning. Knowing what power levels you're looking to achieve so you don't spend $1000 on 555 injectors only to realize you want more power and spending more money on 740's. Same thing can be said about buying down pipes (4 bolt vs 5 bolt configuration) It's been proven that stock turbo's with full breather mods kick ass.