supra with an inline 6 single turbo does pretty good, but the twin turbo kicks ass, there is a pretty big power difference. also my friend has plans to do a twin turbo in his impreza 2.5rs - going to swap in a newer sti engine and add another turbo and it has potential to put out about 500 hpa 4 cylinder doesnt generate enough exhaust gas flow to warrant a twin turbo setup, even on 6 cylinders the effectiveness vs a single turbo properly matched to the size of the engine is iffy at best.
twin turbo's in supra's from the factory are sequential turbossupra with an inline 6 single turbo does pretty good, but the twin turbo kicks ass, there is a pretty big power difference. also my friend has plans to do a twin turbo in his impreza 2.5rs - going to swap in a newer sti engine and add another turbo and it has potential to put out about 500 hp