If i were in your predicament, i would seriously consider selling it and buying a proper matched turbo. As you seem aware, a 3082 is behind the 8 ball, as teh ex wheel is too small to generate enough torque to accelerate the rotating mass quickly. And by using a .63 exhaust, it is partially alliviating that, but adding high backpressure to the equation. I would be fitting a .82 3076, as IMO it is the ideal turbo for an rb25 after 280-300rwkw. Even if you fit the rb30 (which i dont think you will need to)the same turbo can be used, and fry the tyres up to the legal speed limit with more response than you can poke a stick at. If you feel you must have more than 300rwkw, then bite the bullet and get a real gt35r, with a .82internal or you can get away with an external gate .63, but i believe on pump fuel the exhaust backpressure will limit the power to far less than the comp wheel is capable of making. We need something between a gt30 and gt35!