The VF36 is the standard equipment turbocharger used on the JDM V8-V9 Subaru Impreza WRX STI Spec-C. The VF36 is a twin-scroll turbocharger that utilizes the RHF5HB ball bearing CHRA, a P25 exhaust housing, F55 turbine wheel and model 479 compressor wheels as on other STI turbos. It is essentially a twin-scroll VF34.
In order to upgrade USDM WRX/STI setups you will need to utilize the twin-scroll exhaust STI manifold, up pipe and downpipe. As always tuning and other supporting mods are necessary for reliability and performance.