BPU is basic power upgrade. It is accepted on the supra board to be a decat and sports exhaust with a restrictor ring to prevent boost creep. An uprated fuel pump like a walbro or UK spec supra pump. A fuel cut defencer to allow you to boost over 1.0 bar. Maybe a boost controller.
Then theres a plus added for each thing above that like say Water injection, FMIC, HKS or UK higher lift cams, After market piggy back fuel solution say greddy emanage ultimate, bigger injectors, hybrid turbos. Anything that keeps roughly the same configuration without going single turbo really. Wedge some nitrous on top of that little lot and you've got some serious wedge beating ability