[R34 GT-R SKYLINE]

Depending on how much lag you want to put up with there are many options. HKS and GReddy (Trust) make really good turbos as well as Turbonetics. I like the HKS GT2835R (about 400hp) for an overall combination of good power and mininum lag. But if your looking for a big monster turbo the GReddy T88 makes huge power with of course huge lag though.