The factory injectors and fuel pump probably won't be able to deliver once you bolt on the bigger turbo, so you'll want to install some larger ones. Recent-model Subaru cars come with 565cc units. We usually upgrade to 650cc or 750cc units for most street cars, although larger fuel injectors may be appropriate depending on your upgrade plans. E85 (85% ethanol) fuel use requires much larger injectors -- as much as 70% larger than you would otherwise use for gasoline.
In most cases the fuel pump should also be upgraded. The WRX fuel pump has to be replaced with any turbo upgrade. The 2008+ STI pump can supply enough fuel for mild turbo upgrades (up to 20G size on pump gas), but should be upgraded beyond that.
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