The Subaru OEM IHI VF43P turbocharger is a direct bolt-on option for the 02-07 WRX & STI, utilizing the factory mounting points and attaching to the factory oil and coolant lines. This turbo is a great upgrade option for 2.0L WRX owners looking to make significantly more power and still retain OEM quality and fitment. This turbocharger is also compatible with many engine management base maps, eliminating the need for custom tuning in some circumstances. 2.5L WRX models (2006-2007) will also benefit from a VF43p turbo upgrade, however gains will not be as dramatic as on the 2.0 models as the larger displacement motor will suffer from a taper in power in the high RPM range. STI owners should consider this turbocharger as an OEM replacement only. As with all turbo upgrades, this turbo will require fueling and tuning upgrades to operate safely.
The IHI VF43p comes stock on the 2007 STI. It has almost identical features of the VF39 with a thrust bearing and a P18 exhaust housing, but the wastegate opening is larger to relieve boost creep issues. The VF43p is capable of 290 whp on the EJ20.