If you go STI top mount you will also need the undertray to suit otherwise you only use the same amount of core as a WRX. For 330 - I'd say you're about right with the mods, 3 port solenoid as mentioned is a good idea.
The WRX has tumbler valves which restrict airflow and are there to reduce emissions at idle STI's never had them nor did JDM cars. They are in the cast blocks between the Inlet manifold and the heads and are where the injectors are fitted. If you are removing the inlet to change injectors turbo etc. then it's a good idea to remove the valves and port the castings. You will need new gaskets (inlet to tumbler) and tumbler to heads - Personally I'd fit a phenolic gasket with an O ring seal to the heads to reduce heat soak. Also consider a parallel fuel rail setup to further protect the engine while you have it all removed as the standard fueling system can lead to lean running on cylinder 3 (I believe).
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2005 Spec B 6MT - KiDO tuned (~270Bhp)
Custom exhaust - Cosworth filter - Samco Intake - Tints - Bilstein B8/B6 & STI springs - SuperPro ALK - Whiteline positive shift kit, rack mounts, rear adjustable camber bushes, front ARB mounts & strut brace, 20mm rear ARB with AVO mounts, - Hardrace Gearbox and pitch mounts - Prodrive PFF7's - Front Brembos - Kenwood CarPlay - 1/2 carbon grille - STI front splitter