+1 for flex setup. The VF52 is a fairly capable turbo and midrange response is king imo in a low-moderate power street car. Some ethanol should happily see you into the mid to high 200hp range.

If you're happy to sacrifice a little response and don't want to go to flex/e85 you could go with a TD05 20g turbo, again easily good for the 260-300hp region.

CAI won't add much to your setup, but if you want it then put it on with other upgrades to go for a single tune. It will be plenty safe with a good tune, so long as you don't drive through big puddles if it's in your guard.

Wouldn't bother with headers personally for the cost vs reward factor. Again bundle them with other upgrades (flex or new turbo) for better results.

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MY08 WRX 325hp/456nm/18psi E85